Tau Biology, Tauopathy, Traumatic Brain Injury, and Diagnostic Challenges

Advancements in diagnosing Post-concussion Syndrome: insights into epidemiology, pathophysiology, neuropathology, neuroimaging, and salivary biomarkers

Post-Concussion Syndrome (PCS) represents a complex constellation of symptoms that persist following a concussion or mild traumatic brain injury (mTBI), with significant implications for patient care and outcomes. Despite its prevalence, diagnosing PCS presents considerable challenges due to the subjective nature of symptoms, the absence of specific diagnostic tests, and the overlap with other neurological and psychiatric conditions. This review explores the multifaceted diagnostic challenges associated with PCS, including the heterogeneity of symptom presentation, the limitations of current neuroimaging techniques, and the overlap of PCS symptoms with other disorders. We also discuss the potential of emerging biomarkers and advanced imaging modalities to enhance diagnostic accuracy and provide a more objective basis for PCS identification. Additionally, the review highlights the importance of a multidisciplinary approach in the diagnosis and management of PCS, integrating clinical evaluation with innovative diagnostic tools to improve patient outcomes. Through a comprehensive analysis of current practices and future directions, this review aims to shed light on the complexities of PCS diagnosis and pave the way for improved strategies in the identification and treatment of this condition.

Exosomal MicroRNAs in Alzheimer's Disease: Unveiling Their Role and Pioneering Tools for Diagnosis and Treatment

Alzheimer's disease (AD) is a common neurodegenerative disorder that presents a significant health concern, often leading to substantial cognitive decline among older adults. A prominent feature of AD is progressive dementia, which eventually disrupts daily functioning and the ability to live independently. A major challenge in addressing AD is its prolonged pre-symptomatic phase, which makes early detection difficult. Moreover, the disease's complexity and the inefficiency of current diagnostic methods impede the development of targeted therapies. Therefore, there is an urgent need to enhance diagnostic methodologies for detection and treating AD even before clinical symptoms appear. Exosomes are nanoscale biovesicles secreted by cells, including nerve cells, into biofluids. These exosomes play essential roles in the central nervous system (CNS) by facilitating neuronal communication and thus influencing major physiological and pathological processes. Exosomal cargo, particularly microRNAs (miRNAs), are critical mediators in this cellular communication, and their dysregulation affects various pathological pathways related to neurodegenerative diseases, including AD. This review discusses the significant roles of exosomal miRNAs in the pathological mechanisms related to AD, focusing on the promising use of exosomal miRNAs as diagnostic biomarkers and targeted therapeutic interventions for this devastating disease.

Phosphorylated tau 181 (p-tau181) as an innovative, fast and robust biomarker for cerebrospinal fluid leaks

BACKGROUND

Cerebrospinal fluid (CSF) leaks can lead to serious complications if left untreated, making rapid and accurate diagnosis essential. Biomarkers such as β2-transferrin (B2TRF) and β-trace protein are used to detect CSF leaks, but their limitations warrant the exploration of alternative markers. This study investigates the potential of phosphorylated tau at threonine 181 (p-tau181) as a biomarker for CSF leaks.

METHODS

Samples from 56 subjects were analyzed for B2TRF and p-tau181 using immunoaffinity blotting and chemiluminescent enzyme immunoassay, respectively. Data analysis included Mann-Whitney test to assess the overall difference in median p-tau181 concentrations between B2TRF positive and negative patients and a receiver operating characteristic (ROC) curve analysis to determine optimal p-tau181 cutoff values for predicting B2TRF positivity.

RESULTS

p-tau181 levels were significantly higher in B2TRF positive samples compared to negative samples (p < 0.001). ROC analysis showed high diagnostic performance for p-tau181, with an optimal cutoff of 13.22 pg/mL providing 92.0% sensitivity and 93.1% specificity. Excluding hemolyzed samples improved further the diagnostic performances, maintaining high sensitivity (90.9%) and achieving perfect specificity (100.0%).

CONCLUSIONS

This study highlights the potential of p-tau181 as a valuable biomarker for the detection of CSF leaks due to its high diagnostic accuracy and practical advantages over the current biomarkers. The characteristics of p-tau181 assay being both quantitative and rapid, with high diagnostic accuracy, suggest that it could be a valuable tool for the detection of CSF leaks. Further research are now needed to validate these findings.

Evidence for Altered White Matter Organization After Mild Traumatic Brain Injury: A Scoping Review on the Use of Diffusion Magnetic Resonance Imaging and Blood-Based Biomarkers to Investigate Acute Pathology and Relationship to Persistent Post-Concussion Symptoms

Mild traumatic brain injury (mTBI) is the most common form of traumatic brain injury. Post-concussive symptoms typically resolve after a few weeks although up to 20% of people experience these symptoms for >3 months, termed persistent post-concussive symptoms (PPCS). Subtle white matter (WM) microstructural damage is thought to underlie neurological and cognitive deficits experienced post-mTBI. Evidence suggests that diffusion magnetic resonance imaging (dMRI) and blood-based biomarkers could be used as surrogate markers of WM organization. We conducted a scoping review according to PRISMA-ScR guidelines, aiming to collate evidence for the use of dMRI and/or blood-based biomarkers of WM organization, in mTBI and PPCS, and document relationships between WM biomarkers and symptoms. We focused specifically on biomarkers of axonal or myelin integrity post-mTBI. Biomarkers excluded from this review therefore included the following: astroglial, perivascular, endothelial, and inflammatory markers. A literature search performed across four databases, EMBASE, Scopus, Google Scholar, and ProQuest, identified 100 records: 68 analyzed dMRI, 28 assessed blood-based biomarkers, and 4 used both. Blood biomarker studies commonly assessed axonal cytoskeleton proteins (i.e., tau); dMRI studies assessed measures of WM organization (i.e., fractional anisotropy). Significant biomarker alterations were frequently associated with heightened symptom burden and prolonged recovery time post-injury. These data suggest that dMRI and blood-based biomarkers may be useful proxies of WM organization, although few studies assessed these complementary measures in parallel, and the relationship between modalities remains unclear. Further studies are warranted to assess the benefit of a combined biomarker approach in evaluating alterations to WM organization after mTBI.

Serum tau protein and myelin basic protein in pediatric patients with congenital heart defects undergoing cardiac surgery: preliminary assessment as novel neuromarkers of brain injury

INTRODUCTION

Neurological impairment is a big concern in the development of patients with congenital heart defects (CHD). A number of neuromarkers have been studied in search of a diagnostic or prognostic marker for brain injury during the vulnerable perioperative period. Our aim was to assess two novel neuromarkers, myelin basic protein (MBP) and protein Tau (pTau), as diagnostic markers for brain injury in perioperative period in children with CHD.

METHODS

Forty patients were enrolled and dichotomized based on peripheric oxygen saturation in cyanotic and non-cyanotic group. Blood samples were collected preoperative, after the induction of anesthesia, and in postoperative day 1. Neuromarker concentrations were measured using commercially available ELISA kits.

RESULTS

Neuromarkers' values were increased postoperative, with statistical significance reached only in non-cyanotic group (p < 0.0001). A significant positive correlation was observed between preoperatory MBP and albumin level, hemoglobin level, height, and weight of patients. Association with cerebral saturations were analyzed by a coefficient defined as ≥ 20% reduction in cerebral saturation measured by near-infrared spectroscopy during perioperative period. An acceptable predicting model was observed with pTau in cyanotic group (AUC = 0.7).

CONCLUSION

We evaluated MBP and pTau as potential biomarkers of brain injury in children with CHD undergoing cardiac surgery. Elevated postoperative pTau and MBP concentrations were observed in both groups. Elevated pTau values were associated with perioperative hypoxemia.

A Narrative Review of Existing and Developing Biomarkers in Acute Traumatic Brain Injury for Potential Military Deployed Use

INTRODUCTION

Traumatic brain injury (TBI) is a leading cause of morbidity and mortality in both adult civilian and military populations. Currently, diagnostic and prognostic methods are limited to imaging and clinical findings. Biomarker measurements offer a potential method to assess head injuries and help predict outcomes, which has a potential benefit to the military, particularly in the deployed setting where imaging modalities are limited. We determine how biomarkers such as ubiquitin C-terminal hydrolase-L1 (UCH-L1), glial fibrillary acidic protein (GFAP), S100B, neurofilament light chain (NFL), and tau proteins can offer important information to guide the diagnosis, acute management, and prognosis of TBI, specifically in military personnel.

MATERIALS AND METHODS

We performed a narrative review of peer-reviewed literature using online databases of Google Scholar and PubMed. We included articles published between 1988 and 2022.

RESULTS

We screened a total of 73 sources finding a total of 39 original research studies that met inclusion for this review. We found five studies that focused on GFAP, four studies that focused on UCH-L1, eight studies that focused on tau proteins, six studies that focused on NFL, and eight studies that focused on S100B. The remainder of the studies included more than one of the biomarkers of interest.

CONCLUSIONS

TBI occurs frequently in the military and civilian settings with limited methods to diagnose and prognosticate outcomes. We highlighted several promising biomarkers for these purposes including S100B, UCH-L1, NFL, GFAP, and tau proteins. S100B and UCH-L1 appear to have the strongest data to date, but further research is necessary. The robust data that explain the optimal timing and, more importantly, trending of these biomarker measurements are necessary before widespread application.

Elevated Serum Tau and UCHL-1 Concentrations Within 12 Months of Injury Predict Neurobehavioral Functioning 2 or More Years Following Traumatic Brain Injury: A Longitudinal Study

OBJECTIVE

Blood-based biomarkers have received considerable attention for their diagnostic and prognostic value in the acute and postacute period following traumatic brain injury (TBI). The purpose of this study was to examine whether blood-based biomarker concentrations within the first 12 months of TBI can predict neurobehavioral outcome in the chronic phase of the recovery trajectory.

SETTING

Inpatient and outpatient wards from 3 military medical treatment facilities.

PARTICIPANTS

A total of 161 service members and veterans classified into 3 groups: ( a ) uncomplicated mild TBI (MTBI; n = 37), ( b ) complicated mild, moderate, severe, penetrating TBI combined (STBI; n = 46), and ( c ) controls (CTRL; n = 78).

DESIGN

Prospective longitudinal.

MAIN MEASURES

Participants completed 6 scales from the Traumatic Brain Injury Quality of Life (ie, Anger, Anxiety, Depression, Fatigue, Headaches, and Cognitive Concerns) within 12 months (baseline) and at 2 or more years (follow-up) post-injury. Serum concentrations of tau, neurofilament light, glial fibrillary acidic protein, and UCHL-1 at baseline were measured using SIMOA.

RESULTS

Baseline tau was associated with worse anger, anxiety, and depression in the STBI group at follow-up ( R2 = 0.101-0.127), and worse anxiety in the MTBI group ( R2 = 0.210). Baseline ubiquitin carboxyl-terminal hydrolase L1 (UCHL-1) was associated with worse anxiety and depression at follow-up in both the MTBI and STBI groups ( R2 Δ = 0.143-0.207), and worse cognitive concerns in the MTBI group ( R2 Δ = 0.223).

CONCLUSIONS

A blood-based panel including these biomarkers could be a useful tool for identifying individuals at risk of poor outcome following TBI.

Clinical Outcomes After Traumatic Brain Injury and Exposure to Extracranial Surgery: A TRACK-TBI Study

Importance

Traumatic brain injury (TBI) is associated with persistent functional and cognitive deficits, which may be susceptible to secondary insults. The implications of exposure to surgery and anesthesia after TBI warrant investigation, given that surgery has been associated with neurocognitive disorders.

Objective

To examine whether exposure to extracranial (EC) surgery and anesthesia is related to worse functional and cognitive outcomes after TBI.

Design, Setting, and Participants

This study was a retrospective, secondary analysis of data from the Transforming Research and Clinical Knowledge in Traumatic Brain Injury (TRACK-TBI) study, a prospective cohort study that assessed longitudinal outcomes of participants enrolled at 18 level I US trauma centers between February 1, 2014, and August 31, 2018. Participants were 17 years or older, presented within 24 hours of trauma, were admitted to an inpatient unit from the emergency department, had known Glasgow Coma Scale (GCS) and head computed tomography (CT) status, and did not undergo cranial surgery. This analysis was conducted between January 2, 2020, and August 8, 2023.

Exposure

Participants who underwent EC surgery during the index admission were compared with participants with no surgery in groups with a peripheral orthopedic injury or a TBI and were classified as having uncomplicated mild TBI (GCS score of 13-15 and negative CT results [CT- mTBI]), complicated mild TBI (GCS score of 13-15 and positive CT results [CT+ mTBI]), or moderate to severe TBI (GCS score of 3-12 [m/sTBI]).

Main Outcomes and Measures

The primary outcomes were functional limitations quantified by the Glasgow Outcome Scale-Extended for all injuries (GOSE-ALL) and brain injury (GOSE-TBI) and neurocognitive outcomes at 2 weeks and 6 months after injury.

Results

A total of 1835 participants (mean [SD] age, 42.2 [17.8] years; 1279 [70%] male; 299 Black, 1412 White, and 96 other) were analyzed, including 1349 nonsurgical participants and 486 participants undergoing EC surgery. The participants undergoing EC surgery across all TBI severities had significantly worse GOSE-ALL scores at 2 weeks and 6 months compared with their nonsurgical counterparts. At 6 months after injury, m/sTBI and CT+ mTBI participants who underwent EC surgery had significantly worse GOSE-TBI scores (B = -1.11 [95% CI, -1.53 to -0.68] in participants with m/sTBI and -0.39 [95% CI, -0.77 to -0.01] in participants with CT+ mTBI) and performed worse on the Trail Making Test Part B (B = 30.1 [95% CI, 11.9-48.2] in participants with m/sTBI and 26.3 [95% CI, 11.3-41.2] in participants with CT+ mTBI).

Conclusions and Relevance

This study found that exposure to EC surgery and anesthesia was associated with adverse functional outcomes and impaired executive function after TBI. This unfavorable association warrants further investigation of the potential mechanisms and clinical implications that could inform decisions regarding the timing of surgical interventions in patients after TBI.

Blood-Based Biomarkers for Neuroprognostication in Acute Brain Injury

Acute brain injury causes loss of functionality in patients that often is devastating. Predicting the degree of functional loss and overall prognosis requires a multifaceted approach to help patients, and more so their families, make important decisions regarding plans and goals of care. A variety of blood-based markers have been studied as one aspect of this determination. In this review, we discuss CNS-derived and systemic markers that have been studied for neuroprognostication purposes. We discuss the foundation of each protein, the conditions in which it has been studied, and how the literature has used these markers for interpretation. We also discuss challenges to using each marker in each section as well.

Nanowired delivery of antibodies to tau and neuronal nitric oxide synthase together with cerebrolysin attenuates traumatic brain injury induced exacerbation of brain pathology in Parkinson's disease

Concussive head injury (CHI) is one of the major risk factors for developing Parkinson's disease in later life of military personnel affecting lifetime functional and cognitive disturbances. Till date no suitable therapies are available to attenuate CHI or PD induced brain pathology. Thus, further exploration of novel therapeutic agents are highly warranted using nanomedicine in enhancing the quality of life of veterans or service members of US military. Since PD or CHI induces oxidative stress and perturbs neurotrophic factors regulation associated with phosphorylated tau (p-tau) deposition, a possibility exists that nanodelivery of agents that could enhance neurotrophic factors balance and attenuate oxidative stress could be neuroprotective in nature. In this review, nanowired delivery of cerebrolysin-a balanced composition of several neurotrophic factors and active peptide fragments together with monoclonal antibodies to neuronal nitric oxide synthase (nNOS) with p-tau antibodies was examined in PD following CHI in model experiments. Our results suggest that combined administration of nanowired antibodies to nNOS and p-tau together with cerebrolysin significantly attenuated CHI induced exacerbation of PD brain pathology. This combined treatment also has beneficial effects in CHI or PD alone, not reported earlier.

Spatiotemporal profile of atrophy in the first year following moderate-severe traumatic brain injury

Traumatic brain injury (TBI) triggers progressive neurodegeneration resulting in brain atrophy that continues months-to-years following injury. However, a comprehensive characterization of the spatial and temporal evolution of TBI-related brain atrophy remains incomplete. Utilizing a sensitive and unbiased morphometry analysis pipeline optimized for detecting longitudinal changes, we analyzed a sample consisting of 37 individuals with moderate-severe TBI who had primarily high-velocity and high-impact injury mechanisms. They were scanned up to three times during the first year after injury (3 months, 6 months, and 12 months post-injury) and compared with 33 demographically matched controls who were scanned once. Individuals with TBI already showed cortical thinning in frontal and temporal regions and reduced volume in the bilateral thalami at 3 months post-injury. Longitudinally, only a subset of cortical regions in the parietal and occipital lobes showed continued atrophy from 3 to 12 months post-injury. Additionally, cortical white matter volume and nearly all deep gray matter structures exhibited progressive atrophy over this period. Finally, we found that disproportionate atrophy of cortex along sulci relative to gyri, an emerging morphometric marker of chronic TBI, was present as early as 3 month post-injury. In parallel, neurocognitive functioning largely recovered during this period despite this pervasive atrophy. Our findings demonstrate msTBI results in characteristic progressive neurodegeneration patterns that are divergent across regions and scale with the severity of injury. Future clinical research using atrophy during the first year of TBI as a biomarker of neurodegeneration should consider the spatiotemporal profile of atrophy described in this study.

Peripherin: A proposed biomarker of traumatic axonal injury triggered by mechanical force

Traumatic axonal injury (TAI) is one of the most common pathological features of severe traumatic brain injury (TBI). Our previous study using proteomics suggested that peripherin (PRPH) should be a potential candidate as a biomarker for TAI diagnosis. This study is to further elucidate the role and association of PRPH with TAI. In the animal study, we performed immunohistochemistry, ELISA and morphological analysis to evaluate PRPH level and distribution following a severe impact. PRPH-positive regions were widely distributed in the axonal tract throughout the whole brain. Axonal injuries with PRPH inclusion were observed post-TBI. Besides, PRPH was significantly increased in both cerebral spinal fluid and plasma at the early phase post-TBI. Colocalization analysis based on microscopy revealed that PRPH represents an immunohistological biomarker in the neuropathological diagnosis of TAI. Brain samples from patients with TBI were included to further test whether PRPH is feasible in the real practice of neuropathology. Immunohistochemistry of PRPH, NFH, APP and NFL on human brain tissues further confirmed PRPH as an immunohistological biomarker that could be applied in practice. Collectively, we conclude that PRPH mirrors the cytoskeleton injury of axons and could represent a neuropathological biomarker for TAI.

Recent advances in the role of miRNAs in post-traumatic stress disorder and traumatic brain injury

Post-traumatic stress disorder (PTSD) is usually considered a psychiatric disorder upon emotional trauma. However, with the rising number of conflicts and traffic accidents around the world, the incidence of PTSD has skyrocketed along with traumatic brain injury (TBI), a complex neuropathological disease due to external physical force and is also the most common concurrent disease of PTSD. Recently, the overlap between PTSD and TBI is increasingly attracting attention, as it has the potential to stimulate the emergence of novel treatments for both conditions. Of note, treatments exploiting the microRNAs (miRNAs), a well-known class of small non-coding RNAs (ncRNAs), have rapidly gained momentum in many nervous system disorders, given the miRNAs' multitudinous and key regulatory role in various biological processes, including neural development and normal functioning of the nervous system. Currently, a wealth of studies has elucidated the similarities of PTSD and TBI in pathophysiology and symptoms; however, there is a dearth of discussion with respect to miRNAs in both PTSD and TBI. In this review, we summarize the recent available studies of miRNAs in PTSD and TBI and discuss and highlight promising miRNAs therapeutics for both conditions in the future.

Exploring the Therapeutic Potential of Phosphorylated Cis-Tau Antibody in a Pig Model of Traumatic Brain Injury

Traumatic brain injury (TBI) results in the generation of tau. As hyperphosphorylated tau (p-tau) is one of the major consequences of TBI, targeting p-tau in TBI may lead to the development of new therapy. Twenty-five pigs underwent a controlled cortical impact. One hour after TBI, pigs were administered either vehicle (n = 13) or PNT001 (n = 12), a monoclonal antibody for the cis conformer of tau phosphorylated at threonine 231. Plasma biomarkers of neural injury were assessed for 14 days. Diffusion tensor imaging was performed at day 1 and 14 after injury, and these were compared to historical control animals (n = 4). The fractional anisotropy data showed significant white matter injury for groups at 1 day after injury in the corona radiata. At 14 days, the vehicle-treated pigs, but not the PNT001-treated animals, exhibited significant white matter injury compared to sham pigs in the ipsilateral corona radiata. The PNT001-treated pigs had significantly lower levels of plasma glial fibrillary acidic protein (GFAP) at day 2 and day 4. These findings demonstrate a subtle reduction in the areas of white matter injury and biomarkers of neurological injury after treatment with PNT001 following TBI. These findings support additional studies for PNT001 as well as the potential use of this agent in clinical trials in the near future.

The Adult Neurogenesis Theory of Alzheimer's Disease

Alzheimer's disease starts in neural stem cells (NSCs) in the niches of adult neurogenesis. All primary factors responsible for pathological tau hyperphosphorylation are inherent to adult neurogenesis and migration. However, when amyloid pathology is present, it strongly amplifies tau pathogenesis. Indeed, the progressive accumulation of extracellular amyloid-β deposits in the brain triggers a state of chronic inflammation by microglia. Microglial activation has a significant pro-neurogenic effect that fosters the process of adult neurogenesis and supports neuronal migration. Unfortunately, this "reactive" pro-neurogenic activity ultimately perturbs homeostatic equilibrium in the niches of adult neurogenesis by amplifying tau pathogenesis in AD. This scenario involves NSCs in the subgranular zone of the hippocampal dentate gyrus in late-onset AD (LOAD) and NSCs in the ventricular-subventricular zone along the lateral ventricles in early-onset AD (EOAD), including familial AD (FAD). Neuroblasts carrying the initial seed of tau pathology travel throughout the brain via neuronal migration driven by complex signals and convey the disease from the niches of adult neurogenesis to near (LOAD) or distant (EOAD) brain regions. In these locations, or in close proximity, a focus of degeneration begins to develop. Then, tau pathology spreads from the initial foci to large neuronal networks along neural connections through neuron-to-neuron transmission.

Chronic Gq activation of ventral hippocampal neurons and astrocytes differentially affects memory and behavior

Network dysfunction is implicated in numerous diseases and psychiatric disorders, and the hippocampus serves as a common origin for these abnormalities. To test the hypothesis that chronic modulation of neurons and astrocytes induces impairments in cognition, we activated the hM3D(Gq) pathway in CaMKII+ neurons or GFAP+ astrocytes within the ventral hippocampus across 3, 6, and 9 months. CaMKII-hM3Dq activation impaired fear extinction at 3 months and acquisition at 9 months. Both CaMKII-hM3Dq manipulation and aging had differential effects on anxiety and social interaction. GFAP-hM3Dq activation impacted fear memory at 6 and 9 months. GFAP-hM3Dq activation impacted anxiety in the open field only at the earliest time point. CaMKII-hM3Dq activation modified the number of microglia, while GFAP-hM3Dq activation impacted microglial morphological characteristics, but neither affected these measures in astrocytes. Overall, our study elucidates how distinct cell types can modify behavior through network dysfunction, while adding a more direct role for glia in modulating behavior.

Gα13-Mediated Signaling Cascade Is Related to the Tau Pathology Caused by Anesthesia and Surgery in 5XFAD Transgenic Mice

BACKGROUND

Our previous studies indicated that anesthesia and surgery could aggravate cognitive impairment of 5XFAD transgenic (Tg) mice, and this aggravation was associated with tau hyperphosphorylation. We previously identified that GNA13 (the gene encoding Gα13) was a hub gene with tau hyperphosphorylation.

OBJECTIVE

This study aims to further investigate the mechanism that whether the Gα13-mediated signaling pathway acts as an instigator to regulate cofilin activation and autophagy impairment in this process.

METHODS

5XFAD Tg mice and their littermate (LM) mice were randomly allocated into four groups: LM Control group, LM Anesthesia/Surgery group, AD Control group, and AD Anesthesia/Surgery group. For mice in the Anesthesia/Surgery groups, abdominal surgery was performed under 1.4% isoflurane anesthesia followed by sustaining anesthetic inhalation for up to 2 h.

RESULTS

Compared with the AD Control group, protein levels of Gα13, ROCK2, LPAR5, and p-tau/tau46 ratio were increased, while p-cofilin/cofilin protein expression ratio was decreased in the AD Anesthesia/Surgery group. However, the differences in these protein levels were not significant among LM groups.

CONCLUSION

This study demonstrated that anesthesia and surgery might exacerbate p-tau accumulation in 5XFAD Tg mice but not in LM mice. And this might be closely related to cofilin activation via Gα13-mediated signaling cascade.

Neurobiochemical, Peptidomic, and Bioinformatic Approaches to Characterize Tauopathy Peptidome Biomarker Candidates in Experimental Mouse Model of Traumatic Brain Injury

Traumatic brain injury (TBI) is a multidimensional damage, and currently, no FDA-approved medicine is available. Multiple pathways in the cell are triggered through a head injury (e.g., calpain and caspase activation), which truncate tau and generate variable fragment sizes (MW 400-45,000 K). In this study, we used an open-head TBI mouse model generated by controlled cortical impact (CCI) and collected ipsilateral (IC) and contralateral (CC) mice htau brain cortices at one (D1) three (D3), and seven (D7) days post-injury. We implemented immunological (antibody-based detection) and peptidomic approaches (nano-reversed-phase liquid chromatography/tandem mass spectrometry) to investigate proteolytic tau peptidome (low molecular weight (LMW) < 10 K)) and pathological phosphorylation sites (high-molecular-weight (HMW); > 10 K) derived from CCI-TBI animal models. Our immunoblotting analysis verified tau hyperphosphorylation, HMW, and HMW breakdown products (HMW-BDP) formation of tau (e.g., pSer₂₀₂, pThr₁₈₁, pThr₂₃₁, pSer₃₉₆, and pSer₄₀₄), following CCI-TBI. Peptidomic data revealed unique sequences of injury-dependent proteolytic peptides generated from human tau protein. Among the N-terminal tau peptides, EIPEGTTAEEAGIGDTPSLEDEAAGHVTQA (a.a. 96-125) and AQPHTEIPEGTTAEEAGIGDTPSLEDEAAGHVTQARM (a.a. 91-127). Examples of tau C-terminal peptides identified include NVSSTGSIDMVDSPQLATLADEVSASLAKQGL (a.a. 410-441) and QLATLADEVSASLAKQGL (a.a. 424-441). Our peptidomic bioinformatic tools showed the association of proteases, such as CAPN1, CAPN2, and CTSL; CASP1, MMP7, and MMP9; and ELANE, GZMA, and MEP1A, in CCI-TBI tau peptidome. In clinical trials for novel TBI treatments, it might be useful to monitor a subset of tau peptidome as targets for biomarker utility and use them for a "theranostic" approach.

Serum Tau, Neurofilament Light Chain, Glial Fibrillary Acidic Protein, and Ubiquitin Carboxyl-Terminal Hydrolase L1 Are Associated with the Chronic Deterioration of Neurobehavioral Symptoms after Traumatic Brain Injury

The purpose of this study was to examine the association of serum tau, neurofilament light chain (NFL), glial fibrillary acidic protein (GFAP), and ubiquitin carboxy-terminal hydrolase L1 (UCHL-1) concentrations evaluated within the first 12 months after a military-related TBI, with longitudinal changes in neurobehavioral functioning extending two or more years post-injury. Participants were 84 United States service members and veterans (SMVs) prospectively enrolled in the Defense and Veterans Brain Injury Center of Excellence/Traumatic Brain Injury Center 15-Year Longitudinal TBI Study, separated into three discreet groups: (a) uncomplicated mild TBI (MTBI; n = 28), (b) complicated mild, moderate, severe, and penetrating TBI combined (STBI; n = 29], and (c) non-injured controls (NIC, n = 27). Participants completed a battery of self-report neurobehavioral symptom measures (e.g., depression, post-traumatic stress disorder [PTSD], post-concussion, anxiety, somatic, cognitive, and neurological symptoms) within 12 months of injury (baseline), and then again at two or more years post-injury (follow-up). At baseline, participants also completed a blood draw to determine serum concentrations of tau, NFL, GFAP, and UCHL-1 using an ultra-sensitivity assay method. In the MTBI and STBI groups (using hierarchical regression analyses), (1) baseline tau concentrations predicted the deterioration of neurobehavioral symptoms from baseline to follow-up on measures of anxiety, PTSD, depression, post-concussion, somatic, and neurological symptoms (accounting for 10-28% of the variance); (2) NFL predicted the deterioration of depression, post-concussion, somatic, cognitive, and neurological symptoms (10-32% variance); (3) GFAP predicted the deterioration of post-concussion, PTSD, depression, anxiety, somatic, neurological, and cognitive symptoms (11-43% variance); and (4) UCHL-1 predicted the deterioration of anxiety, somatic, and neurological symptoms (10-16% variance). In the NIC group, no meaningful associations were found between baseline biomarker concentrations and the deterioration of neurobehavioral symptoms on the majority of measures. This study reports that elevated tau, NFL, GFAP, and UCHL-1 concentrations within the first 12 months of injury are associated with the deterioration of neurobehavioral symptoms that extends to the chronic phase of recovery after a TBI. These findings suggest that a blood-based panel including these biomarkers could be a useful prognostic tool to identifying those individuals at risk of poor future outcome after TBI.

Nasal administration of mesenchymal stem cells prevents accelerated age-related tauopathy after chemotherapy in mice

BACKGROUND

There is increasing concern that cancer and cancer treatment accelerate aging and the associated cognitive decline. We showed recently that treatment of 9-month-old male mice with cisplatin causes cognitive deficits that are associated with formation of tau deposits in the hippocampus. Here we explored the capacity of mesenchymal stem cells (MSC) given via the nose to prevent age-related brain tau deposits. Moreover, we more closely examined the cellular distribution of this hallmark of accelerated brain aging in response to treatment of 9-month-old female and male mice with cisplatin.

RESULTS

We show that cisplatin induces tau deposits in the entorhinal cortex and hippocampus in both sexes. The tau deposits colocalize with syndecan-2. Astrocytes surrounding tau deposits have increased glial fibrillary acidic protein glial fibrillary acidic protein (GFAP) expression. Most of the cisplatin-induced tau deposits were located in microtubule associated protein-2 (MAP-2)⁺ neurons that were surrounded by aquaporin 4⁺ (AQP4)⁺ neuron-facing membrane domains of astrocytes. In addition, some tau deposits were detected in the perinuclear region of GFAP⁺ astrocytes and in CD31⁺ endothelial cells. There were no morphological signs of activation of ionized calcium binding adaptor molecule-1⁺ (Iba-1)⁺ microglia and no increases in brain cytokine production. Nasal administration of MSC at 48 and 96 hours after cisplatin prevented formation of tau deposits and normalized syndecan-2 and GFAP expression. Behaviorally, cisplatin-induced tau cluster formation was associated with reduced executive functioning and working/spatial memory and nasal administration of MSC at 48 and 96 hours after cisplatin prevented these cognitive deficits. Notably, delayed MSC administration (1 month after cisplatin) also prevented tau cluster formation and cognitive deficits, in both sexes.

CONCLUSION

In summary, nasal administration of MSC to older mice at 2 days or 1 month after completion of cisplatin treatment prevents the accelerated development of tau deposits in entorhinal cortex and hippocampus and the associated cognitive deficits. Since MSC are already in clinical use for many other clinical indications, developing nasal MSC administration for treatment of accelerated brain aging and cognitive deficits in cancer survivors should be feasible and would greatly improve their quality of life.

Tau as a fluid biomarker of concussion and neurodegeneration

Concussion is predominant among the vast number of traumatic brain injuries that occur worldwide. Difficulties in timely identification, whether concussion led to neuronal injury or not, diagnosis and the lack of prognostic tools for adequate management could lead this type of brain injury to progressive neurodegenerative diseases. Tau has been extensively studied in recent years, particularly in repetitive mild traumatic brain injuries and sports-related concussions. Tauopathies, the group of neurodegenerative diseases, have also been studied with advanced functional imaging. Nevertheless, neurodegenerative diseases, such as chronic traumatic encephalopathy, are still conclusively diagnosed at autopsy. Here, we discuss the diagnostic dilemma and the relationship between concussion and neurodegenerative diseases and review the literature on tau as a promising biomarker for concussion.

Diaminocyclopentane-derived O-GlcNAcase inhibitors for combating tau hyperphosphorylation in Alzheimer's disease

We developed potent and selective aminocyclopentane-derived inhibitors of human O-N-acetyl-β-D-glucosaminidase (OGA) implicated in Alzheimer's disease. For example compound 13 was a nanomolar OGA inhibitor with 92 000-fold selectivity over human HexB. It was non-toxic and increased protein O-GlcNAcylation in the culture of murine neural cells, showing new alternatives in the treatment of tauopathies.

Protective Effects of Polysaccharides in Neurodegenerative Diseases

Neurodegenerative diseases (NDs) are characterized by progressive degeneration and necrosis of neurons, including Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease and others. There are no existing therapies that correct the progression of these diseases, and current therapies provide merely symptomatic relief. The use of polysaccharides has received significant attention due to extensive biological activities and application prospects. Previous studies suggest that the polysaccharides as a candidate participate in neuronal protection and protect against NDs. In this review, we demonstrate that various polysaccharides mediate NDs, and share several common mechanisms characterized by autophagy, apoptosis, neuroinflammation, oxidative stress, mitochondrial dysfunction in PD and AD. Furthermore, this review reveals potential role of polysaccharides in vitro and in vivo models of NDs, and highlights the contributions of polysaccharides and prospects of their mechanism studies for the treatment of NDs. Finally, we suggest some remaining questions for the field and areas for new development.

Brain Biomarkers in Patients with COVID-19 and Neurological Manifestations: A Narrative Review

Acute hyperinflammatory response (cytokine storm) and immunosuppression are responsible for critical illness in patients infected with coronavirus disease 2019 (COVID-19). It is a serious public health crisis that has affected millions of people worldwide. The main clinical manifestations are mostly by respiratory tract involvement and have been extensively researched. Increasing numbers of evidence from emerging studies point out the possibility of neurological involvement by COVID-19 highlighting the need for developing technology to diagnose, manage, and treat brain injury in such patients. Here, we aimed to discuss the rationale for the use of an emerging spectrum of blood biomarkers to guide future diagnostic strategies to mitigate brain injury-associated morbidity and mortality risks in COVID-19 patients, their use in clinical practice, and prediction of neurological outcomes.

Aptamers Targeting Hallmark Proteins of Neurodegeneration

Neurodegeneration is a progressive deterioration of neural structures leading to cognitive or motor impairment of the affected patient. There is still no effective therapy for any of the most common neurodegenerative diseases (NDs) such as Alzheimer's or Parkinson's disease. Although NDs exhibit distinct clinical characteristics, many are characterized by the accumulation of misfolded proteins or peptide fragments in the brain and/or spinal cord. The presence of similar inclusion bodies in patients with diverse NDs provides a rationale for developing therapies directed at overlapping disease mechanisms. A novel targeting strategy involves the use of aptamers for therapeutic development. Aptamers are short nucleic acid ligands able to recognize molecular targets with high specificity and high affinity. Despite the fact that several academic groups have shown that aptamers have the potential to be used in therapeutic and diagnostic applications, their clinical translation is still limited. In this study, we describe aptamers that have been developed against proteins relevant to NDs, including prion protein and amyloid beta (Aβ), cell surface receptors and other cytoplasmic proteins. This review also describes advances in the application of these aptamers in imaging, protein detection, and protein quantification, and it provides insights about their accelerated clinical use for disease diagnosis and therapy.

Disclosing tau tangles using PET imaging: a pharmacological review of the radiotracers available in 2021

Neurological symptoms depend on the topography of the lesions in the nervous system, hence the importance of brain imaging for neurologists. Neurological treatment, however, depends on the biological nature of the lesions. The development of radiotracers specific for the proteinopathies observed in neurodegenerative disorders is, therefore, crucially important for better understanding the relationships between the pathology and the clinical symptoms, as well as the efficacy of therapeutical interventions. The tau protein is involved in several neurodegenerative disorders, that can be distinguished both biologically and clinically as the type of tau isoforms and filaments observed in brain aggregates, and the brain regions affected differ between tauopathies. Over the past few years, several tracers have been developed for imaging tauopathies with positron emission tomography. The present review aims to compare the binding properties of these tracers, with a specific focus on how these properties might be relevant for neurologists using these biomarkers to characterize the pathology of patients presenting with clinical symptoms suspect of a neurodegenerative disorder.

Post-Traumatic Epilepsy and Comorbidities: Advanced Models, Molecular Mechanisms, Biomarkers, and Novel Therapeutic Interventions

Post-traumatic epilepsy (PTE) is one of the most devastating long-term, network consequences of traumatic brain injury (TBI). There is currently no approved treatment that can prevent onset of spontaneous seizures associated with brain injury, and many cases of PTE are refractory to antiseizure medications. Post-traumatic epileptogenesis is an enduring process by which a normal brain exhibits hypersynchronous excitability after a head injury incident. Understanding the neural networks and molecular pathologies involved in epileptogenesis are key to preventing its development or modifying disease progression. In this article, we describe a critical appraisal of the current state of PTE research with an emphasis on experimental models, molecular mechanisms of post-traumatic epileptogenesis, potential biomarkers, and the burden of PTE-associated comorbidities. The goal of epilepsy research is to identify new therapeutic strategies that can prevent PTE development or interrupt the epileptogenic process and relieve associated neuropsychiatric comorbidities. Therefore, we also describe current preclinical and clinical data on the treatment of PTE sequelae. Differences in injury patterns, latency period, and biomarkers are outlined in the context of animal model validation, pathophysiology, seizure frequency, and behavior. Improving TBI recovery and preventing seizure onset are complex and challenging tasks; however, much progress has been made within this decade demonstrating disease modifying, anti-inflammatory, and neuroprotective strategies, suggesting this goal is pragmatic. Our understanding of PTE is continuously evolving, and improved preclinical models allow for accelerated testing of critically needed novel therapeutic interventions in military and civilian persons at high risk for PTE and its devastating comorbidities.

Tau nuclear translocation is a leading step in tau pathology process through P53 stabilization and nucleolar dispersion

Tau protein abnormalities are associated with various neurodegenerative disorders, including Alzheimer's disease (AD) and traumatic brain injury (TBI). In tau-overexpressing SHSY5Y cells and iPSC-derived neuron models of frontotemporal dementia (FTD), axonal tau translocates into the nuclear compartment, resulting in neuronal dysfunction. Despite extensive research, the mechanisms by which tau translocation results in neurodegeneration remain elusive thus far. We studied the nuclear displacement of different P-tau species [Cis phosphorylated Thr231-tau (cis P-tau), phosphorylated Ser202/Thr205-tau (AT8 P-tau), and phosphorylated Thr212/Ser214-tau (AT100 P-tau)] at various time points using starvation in primary cortical neurons and single severe TBI (ssTBI) in male mouse cerebral cortices as tauopathy models. While all P-tau species translocated into the somatodendritic compartment in response to stress, cis P-tau did so more rapidly than the other species. Notably, nuclear localization of P-tau was associated with p53 apoptotic stabilization and nucleolar stress, both of which resulted in neurodegeneration. In summary, our findings indicate that P-tau nuclear translocation results in p53-dependent apoptosis and nucleolar dispersion, which is consistent with neurodegeneration.

Developing Biomarkers of Mild Traumatic Brain Injury: Promise and Progress of CNS-Derived Exosomes

Mild traumatic brain injuries (mTBI) are common injuries across civilian and military populations. Although most individuals recover after mTBI, some individuals continue to show long-term symptoms as well as increased risk for neurodegenerative and neuropsychiatric disorders. Currently, diagnosing TBI severity relies primarily on self-report and subjective symptoms, with limited tools for diagnosis or prognosis. Brain-derived exosomes, a form of extracellular vesicle, may offer a solution for interpreting injury states by aiding in diagnosis as well as outcome prediction with relatively low patient burden. Exosomes, which are released into circulation, contain both protein and RNA cargo that can be isolated and quantified, providing a molecular window into molecular status of the exosome source. Here we examined the current literature studying the utility of exosomes, in particular neuronal- and astrocyte-derived exosomes, to identify protein and miRNA biomarkers of injury severity, trajectory, and functional outcome. Current evidence supports the potential for these emerging new tools to capture an accessible molecular window into the brain as it responds to a traumatic injury, however a number of limitations must be addressed in future studies. Most current studies are relatively small and cross sectional; prospective, longitudinal studies across injury severity, and populations are needed to track exosome cargo changes after injury. Standardized exosome isolation as well as advancement in identifying/isolating exosomes from CNS-specific tissue sources will improve mechanistic understanding of cargo changes as well as reliability of findings. Exosomes are also just beginning to be used in model systems to understand functional effects of TBI-associated cargo such as toxicity. Finally linking exosome cargo changes to objective markers of neuronal pathology and cognitive changes will be critical in validating these tools to provide insights into injury and recovery states after TBI.

Cerebrospinal fluid p-tau231 as an early indicator of emerging pathology in Alzheimer's disease

BACKGROUND

Phosphorylated tau (p-tau) epitopes in cerebrospinal fluid (CSF) are accurate biomarkers for a pathological and clinical diagnosis of Alzheimer's disease (AD) and are seen to be increased in preclinical stage of the disease. However, it is unknown if these increases transpire earlier, prior to amyloid-beta (Aβ) positivity as determined by position emission tomography (PET), and if an ordinal sequence of p-tau epitopes occurs at this incipient phase METHODS: We measured CSF concentrations of p-tau181, p-tau217 and p-tau231 in 171 participants across the AD continuum who had undergone Aβ ([¹⁸F]AZD4694) and tau ([¹⁸F]MK6240) position emission tomography (PET) and clinical assessment FINDINGS: All CSF p-tau biomarkers were accurate predictors of cognitive impairment but CSF p-tau217 demonstrated the largest fold-changes in AD patients in comparison to non-AD dementias and cognitively unimpaired individuals. CSF p-tau231 and p-tau217 predicted Aβ and tau to a similar degree but p-tau231 attained abnormal levels first. P-tau231 was sensitive to the earliest changes of Aβ in the medial orbitofrontal, precuneus and posterior cingulate before global Aβ PET positivity was reached INTERPRETATION: We demonstrate that CSF p-tau231 increases early in development of AD pathology and is a principal candidate for detecting incipient Aβ pathology for therapeutic trial application FUNDING: Canadian Institutes of Health Research (CIHR), Canadian Consortium of Neurodegeneration and Aging, Weston Brain Institute, Brain Canada Foundation, the Fonds de Recherche du Québec.

Correlation analysis of miRNA-124, miRNA-210 with brain injury and inflammatory response in patients with craniocerebral injury

OBJECTIVE

To explore the correlation of serum levels of microRNA (miRNA)-124 and miRNA-210 with brain injury and inflammatory response (IR) in patients with craniocerebral injury (CI) at early stage.

MATERIAL AND METHODS

Clinical data of 105 patients with CI (case group) admitted to our hospital from January 2018 to January 2020 were retrospectively analyzed. The other 60 non-CI healthy patients underwent physical examination were selected as the healthy group. The serum levels of miRNA-124 and miRNA-210 were detected by real-time fluorescence quantitative polymerase chain reaction (RT-PCR).

RESULTS

The levels of serum miRNA-124 and miRNA-210 as well as the inflammatory molecules Janus kinase 2 (JAK2), signal transducer and activator of transcription 3 (STAT3), MEK, and extracellular signal-regulated kinases 1/2 (ERK1/2) in the peripheral blood of the case group were higher than those in the healthy group (P<0.05). Additionally, the serum levels of ubiquitin carboxy-terminal hydrolase L1 (UCH-L1), glial fibrillary acidic protein (GFAP), S100B, Tau, macrophage inflammatory protein-1α (MIP-1α), interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α) in the case group were higher than those in the healthy group (P<0.05). The levels of miRNA-124 and miRNA-210 were positively correlated with the serum levels of UCH-L1, GFAP, S100B, Tau, MIP-1α, IL-1β, IL-6, and TNF-α (P<0.05) as well as with the levels of JAK2, STAT3, MEK, and ERK1/2 in the peripheral blood (P<0.05).

CONCLUSION

The elevated levels of serum miRNA-124 and miRNA-210 in patients with CI are closely related to the aggravation of brain injury, overactivation of the IR, and prognosis.

Extracellular vesicles as distinct biomarker reservoirs for mild traumatic brain injury diagnosis

Mild traumatic brain injury does not currently have a clear molecular diagnostic panel to either confirm the injury or to guide its treatment. Current biomarkers for traumatic brain injury rely mainly on detecting circulating proteins in blood that are associated with degenerating neurons, which are less common in mild traumatic brain injury, or with broad inflammatory cascades which are produced in multiple tissues and are thus not brain specific. To address this issue, we conducted an observational cohort study designed to measure a protein panel in two compartments—plasma and brain-derived extracellular vesicles—with the following hypotheses: (i) each compartment provides independent diagnostic information and (ii) algorithmically combining these compartments accurately classifies clinical mild traumatic brain injury. We evaluated this hypothesis using plasma samples from mild (Glasgow coma scale scores 13–15) traumatic brain injury patients (n = 47) and healthy and orthopaedic control subjects (n = 46) to evaluate biomarkers in brain-derived extracellular vesicles and plasma. We used our Track Etched Magnetic Nanopore technology to isolate brain-derived extracellular vesicles from plasma based on their expression of GluR2, combined with the ultrasensitive digital enzyme-linked immunosorbent assay technique, Single-Molecule Array. We quantified extracellular vesicle-packaged and plasma levels of biomarkers associated with two categories of traumatic brain injury pathology: neurodegeneration and neuronal/glial damage (ubiquitin C-terminal hydrolase L1, glial fibrillary acid protein, neurofilament light and Tau) and inflammation (interleukin-6, interleukin-10 and tumour necrosis factor alpha). We found that GluR2+ extracellular vesicles have distinct biomarker distributions than those present in the plasma. As a proof of concept, we showed that using a panel of biomarkers comprised of both plasma and GluR2+ extracellular vesicles, injured patients could be accurately classified versus non-injured patients.

Current directions in tau research: Highlights from Tau 2020

Studies supporting a strong association between tau deposition and neuronal loss, neurodegeneration, and cognitive decline have heightened the allure of tau and tau-related mechanisms as therapeutic targets. In February 2020, leading tau experts from around the world convened for the first-ever Tau2020 Global Conference in Washington, DC, co-organized and cosponsored by the Rainwater Charitable Foundation, the Alzheimer's Association, and CurePSP. Representing academia, industry, government, and the philanthropic sector, presenters and attendees discussed recent advances and current directions in tau research. The meeting provided a unique opportunity to move tau research forward by fostering global partnerships among academia, industry, and other stakeholders and by providing support for new drug discovery programs, groundbreaking research, and emerging tau researchers. The meeting also provided an opportunity for experts to present critical research-advancing tools and insights that are now rapidly accelerating the pace of tau research.

Stress Granules Modulate SYK to Cause Tau-Associated Neurocognitive Deterioration in 5XFAD Mouse After Anesthesia and Surgery

Background

Alzheimer’s disease (AD) is the most common type of dementia. However, no curative therapy has been found effective to slow down the process of AD. It is reported that anesthesia and surgery will induce neurocognitive deterioration in AD, but the mechanism is not quite clear. In this study, we aim to compare the cognitive impairment between 5XFAD transgenic (Tg) mice and its littermate (LM) after isoflurane anesthesia and surgery to clarify the specific impacts of anesthesia and surgery on individuals with AD and to explore the mechanisms.

Methods

We performed abdominal surgery in cognitively impaired, 4-month-old female 5XFAD mice and LM control mice. Isoflurane anesthesia (1.4%) was induced and maintained over 2 h. Open field and fear conditioning tests were conducted on 1, 3 and 7 days after anesthesia and surgery. The total distance, velocity and freezing time were the major outcomes. P-tau (AT8), tau oligomers (T22), stress granules (SGs), the SYK tyrosine kinase and p-SYK in the hippocampus at postoperative day 1 were evaluated by Western Blot assays. The colocalization of SGs, SYK, p-SYK, and neurons in the hippocampus section was assessed using qualitative immunofluorescence.

Results

In the open field test, no difference between the distance moved and the velocity of LM mice and 5XFAD Tg mice were found on day 1 after anesthesia and surgery. 5XFAD Tg mice exhibited reduced freezing time of fear conditioning context test on postoperative day 3, but not on day 7; the LM mice showed no changes in FCTs. Furthermore, p-tau, tau oligomers, SGs, SYK and p-SYK were evident in the hippocampus region of 5XFAD Tg mice on a postoperative day 1. In addition, SGs, SYK, p-SYK were colocalized with hippocampus neurons, as shown by immunofluorescence.

Conclusion

This study demonstrates that anesthesia and surgery may induce tau-associated neurocognitive deterioration in individuals with AD. The mechanism under it may be associated with SGs and the tyrosine kinase, SYK. After anesthesia and surgery, in 5XFAD Tg mice, SGs were formed and SYK was phosphorylated, which may contribute to the phosphorylation of tau protein. This study provided hints that individuals with AD may be more vulnerable to anesthesia and surgery.

Small Neuron-Derived Extracellular Vesicles from Individuals with Down Syndrome Propagate Tau Pathology in the Wildtype Mouse Brain

Individuals with Down syndrome (DS) exhibit Alzheimer's disease (AD) pathology at a young age, including amyloid plaques and neurofibrillary tangles (NFTs). Tau pathology can spread via extracellular vesicles, such as exosomes. The cargo of neuron-derived small extracellular vesicles (NDEVs) from individuals with DS contains p-Tau at an early age. The goal of the study was to investigate whether NDEVs isolated from the blood of individuals with DS can spread Tau pathology in the brain of wildtype mice. We purified NDEVs from the plasma of patients with DS-AD and controls and injected small quantities using stereotaxic surgery into the dorsal hippocampus of adult wildtype mice. Seeding competent Tau conformers were amplified in vitro from DS-AD NDEVs but not NDEVs from controls. One month or 4 months post-injection, we examined Tau pathology in mouse brains. We found abundant p-Tau immunostaining in the hippocampus of the mice injected with DS-AD NDEVs compared to injections of age-matched control NDEVs. Double labeling with neuronal and glial markers showed that p-Tau staining was largely found in neurons and, to a lesser extent, in glial cells and that p-Tau immunostaining was spreading along the corpus callosum and the medio-lateral axis of the hippocampus. These studies demonstrate that NDEVs from DS-AD patients exhibit Tau seeding capacity and give rise to tangle-like intracellular inclusions.

Divergence in the epidemiological estimates of traumatic brain injury in the United States: comparison of two national databases

OBJECTIVE

Traumatic brain injury (TBI) is a leading cause of morbidity and mortality in the US, but the true incidence of TBI is unknown.

METHODS

The National Trauma Data Bank National Sample Program (NTDB NSP) was queried for 2007 and 2013, and population-based weighted estimates of TBI-related emergency department (ED) visits, hospitalizations, and deaths were calculated. These data were compared to the 2017 Centers for Disease Control and Prevention (CDC) report on TBI, which used the Healthcare Cost and Utilization Project's National ("Nationwide" before 2012) Inpatient Sample and National Emergency Department Sample.

RESULTS

In the NTDB NSP the incidence of TBI-related ED visits was 59/100,000 in 2007 and 62/100,000 in 2013. However, in the CDC report there were 534/100,000 in 2007 and 787/100,000 in 2013. The CDC estimate for ED visits was 805% higher in 2007 and 1169% higher in 2013. In the NTDB NSP, the incidence of TBI-related deaths was 5/100,000 in 2007 and 4/100,000 in 2013. In the CDC report, the incidence was 18/100,000 in both years. The CDC estimate for deaths was 260% higher in 2007 and 325% higher in 2013.

CONCLUSIONS

The databases disagreed widely in their weighted estimates of TBI incidence: CDC estimates were consistently higher than NTDB NSP estimates, by an average of 448%. Although such a discrepancy may be intuitive, this is the first study to quantify the magnitude of disagreement between these databases. Given that research, funding, and policy decisions are made based on these estimates, there is a need for a more accurate estimate of the true national incidence of TBI.

Effects of altered tau expression on dentate granule cell excitability in mice

Tauopathies, including Alzheimer's disease, are characterized by progressive accumulation of hyperphosphorylated and pathologic tau protein in association with onset of cognitive and behavioral impairment. Tau pathology is also associated with increased susceptibility to seizures and epilepsy, with tau^-/- mice showing seizure resistance in some epilepsy models. To better understand how tau pathology is related to neuronal excitability, we performed whole-cell patch-clamp electrophysiology in dentate gyrus granule cells of tau^-/- and human-tau expressing, htau mice. The htau mouse is unique from other transgenic tau models in that the endogenous murine tau gene has been and replaced with readily phosphorylated human tau. We assessed several measures of neuronal excitability, including evoked action potential frequency and excitatory synaptic responses in dentate granule cells from tau^-/-, htau, and non-transgenic control mice at 1.5, 4, and 9 months of age. Compared to age matched controls, dentate granule cells from both tau^-/- and htau mice had a lower peak frequency of evoked action potentials and greater paired pulse facilitation, suggesting reduced neuronal excitability. Our results suggest that neuronal excitability is more strongly influenced by the absence of functional tau than by the presence of pathologic tau. These results also suggest that tau's effect on neuronal excitability is more complex than previously understood.

Inhibition of death-associated protein kinase 1 attenuates cis P-tau and neurodegeneration in traumatic brain injury

Traumatic brain injury (TBI) is the leading cause of mortality and disability in young people and may lead to the development of progressive neurodegeneration, such as that observed in chronic traumatic encephalopathy. We have recently found that the conformation-specific cis phosphorylated form of tau (cis P-tau) is a major early driver of neurodegeneration after TBI. However, not much is known about how cis P-tau is regulated in TBI. In this study, we demonstrated a novel critical role of death-associated protein kinase 1 (DAPK1) in regulating cis P-tau induction after TBI. We found that DAPK1 is significantly upregulated in mouse brains after TBI and subsequently promotes cis P-tau induction. Genetic deletion of DAPK1 in mice not only significantly decreases cis P-tau expression, but also effectively attenuates neuropathology development and rescues behavioral impairments after TBI. Mechanistically, DAPK1-mediated cis P-tau induction is regulated by the phosphorylation of Pin1 at Ser71, a unique prolyl isomerase known to control the conformational status of P-tau. Furthermore, pharmacological suppression of DAPK1 kinase activity dramatically decreases the levels of Pin1 phosphorylated at Ser71 as well as cis P-tau after neuronal stress. Thus, DAPK1 is a novel regulator of TBI that, in combination with its downstream targets, has a major impact on the development and/or outcome of TBI, and targeting DAPK1 might offer a potential therapeutic impact on TBI-related neurodegenerative diseases.

Plasma p-tau231: a new biomarker for incipient Alzheimer's disease pathology

The quantification of phosphorylated tau in biofluids, either cerebrospinal fluid (CSF) or plasma, has shown great promise in detecting Alzheimer's disease (AD) pathophysiology. Tau phosphorylated at threonine 231 (p-tau231) is one such biomarker in CSF but its usefulness as a blood biomarker is currently unknown. Here, we developed an ultrasensitive Single molecule array (Simoa) for the quantification of plasma p-tau231 which was validated in four independent cohorts (n = 588) in different settings, including the full AD continuum and non-AD neurodegenerative disorders. Plasma p-tau231 was able to identify patients with AD and differentiate them from amyloid-β negative cognitively unimpaired (CU) older adults with high accuracy (AUC = 0.92-0.94). Plasma p-tau231 also distinguished AD patients from patients with non-AD neurodegenerative disorders (AUC = 0.93), as well as from amyloid-β negative MCI patients (AUC = 0.89). In a neuropathology cohort, plasma p-tau231 in samples taken on avergae 4.2 years prior to post-mortem very accurately identified AD neuropathology in comparison to non-AD neurodegenerative disorders (AUC = 0.99), this is despite all patients being given an AD dementia diagnosis during life. Plasma p-tau231 was highly correlated with CSF p-tau231, tau pathology as assessed by [18F]MK-6240 positron emission tomography (PET), and brain amyloidosis by [18F]AZD469 PET. Remarkably, the inflection point of plasma p-tau231, increasing as a function of continuous [18F]AZD469 amyloid-β PET standardized uptake value ratio, was shown to be earlier than standard thresholds of amyloid-β PET positivity and the increase of plasma p-tau181. Furthermore, plasma p-tau231 was significantly increased in amyloid-β PET quartiles 2-4, whereas CSF p-tau217 and plasma p-tau181 increased only at quartiles 3-4 and 4, respectively. Finally, plasma p-tau231 differentiated individuals across the entire Braak stage spectrum, including Braak staging from Braak 0 through Braak I-II, which was not observed for plasma p-tau181. To conclude, this novel plasma p-tau231 assay identifies the clinical stages of AD and neuropathology equally well as plasma p-tau181, but increases earlier, already with subtle amyloid-β deposition, prior to the threshold for amyloid-β PET positivity has been attained, and also in response to early brain tau deposition. Thus, plasma p-tau231 is a promising novel biomarker of emerging AD pathology with the potential to facilitate clinical trials to identify vulnerable populations below PET threshold of amyloid-β positivity or apparent entorhinal tau deposition.

Brain Injury and Later-Life Cognitive Impairment and Neuropathology: The Honolulu-Asia Aging Study

BACKGROUND

Findings are inconsistent regarding the role of traumatic head injury in the subsequent development of neurologic outcomes.

OBJECTIVE

Examine the relationship between head injury and later cognitive impairment.

METHODS

A sample of 3,123 Japanese-American men was assessed for history of head injury and evaluated for cognitive impairment using the Cognitive Abilities Screening Instrument (CASI). For a subsample of 676 respondents, neuropathologic results from those with and without head injury were compared.

RESULTS

Although the crude model showed an association between history of head injury and later severe cognitive impairment, the relationship lost significance in the adjusted model (OR = 1.320, CI: 0.90-1.93), regardless of time between injury and impairment. Similar to cognitive impairment, hippocampal sclerosis was observed significantly more in the brains of respondents with a history of head injury in the crude model, but the relationship weakened in the adjusted model (OR = 1.462, CI: 0.68-3.12). After adjustment, decedents with a head injury demonstrated marginally higher brain weight (OR = 1.003, CI: 1.00-1.01).

CONCLUSION

We did not find a relationship between head injury and subsequent cognitive decline in this cohort. The neuropathology results also displayed no strong association between history of head injury and specific brain lesions and characteristics. These results support other findings in prospective cohorts. However, they could be influenced by the demographic make-up of the sample (male Japanese-Americans) or by the observation that the majority reported only a single head injury.

Molecular and Diffusion Tensor Imaging Biomarkers of Traumatic Brain Injury: Principles for Investigation and Integration

The last 20 years have seen the advent of new technologies that enhance the diagnosis and prognosis of traumatic brain injury (TBI). There is recognition that TBI affects the brain beyond initial injury, in some cases inciting a progressive neuropathology that leads to chronic impairments. Medical researchers are now searching for biomarkers to detect and monitor this condition. Perhaps the most promising developments are in the biomolecular and neuroimaging domains. Molecular assays can identify proteins indicative of neuronal injury and/or degeneration. Diffusion imaging now allows sensitive evaluations of the brain's cellular microstructure. As the pace of discovery accelerates, it is important to survey the research landscape and identify promising avenues of investigation. In this review, we discuss the potential of molecular and diffusion tensor imaging (DTI) biomarkers in TBI research. Integration of these technologies could advance models of disease prognosis, ultimately improving care. To date, however, few studies have explored relationships between molecular and DTI variables in patients with TBI. Here, we provide a short primer on each technology, review the latest research, and discuss how these biomarkers may be incorporated in future studies.

Molecular mechanisms in Alzheimer's disease and the impact of physical exercise with advancements in therapeutic approaches

Alzheimer's disease (AD) is one of the most common, severe neurodegenerative brain disorder characterized by the accumulation of amyloid-beta plaques, neurofibrillary tangles in the brain causing neural disintegration, synaptic dysfunction, and neuronal death leading to dementia. Although many US-FDA-approved drugs like Donepezil, Rivastigmine, Galantamine are available in the market, their consumption reduces only the symptoms of the disease but fails in potency to cure the disease. This disease affects many individuals with aging. Combating the disease tends to be very expensive. This review focuses on biochemical mechanisms in the neuron both at normal and AD state with relevance to the tau hypothesis, amyloid hypothesis, the risk factors influencing dementia, oxidative stress, and neuroinflammation altogether integrated with neurodegeneration. A brief survey is carried out on available biomarkers in the diagnosis of the disease, drugs used for the treatment, and the challenges in approaching therapeutic targets in inhibiting the disease pathologies. This review conjointly assesses the demerits with the inefficiency of drugs to reach targets, their side effects, and toxicity. Optimistically, this review directs on the advantageous strategies in using nanotechnology-based drug delivery systems to cross the blood-brain barrier for improving the efficacy of drugs combined with a novel neuronal stem cell therapy approach. Determinately, this review aims at the natural, non-therapeutic healing impact of physical exercise on different model organisms and the effect of safe neuromodulation treatments using repetitive Transcranial Magnetic Stimulation (rTMS), transcranial Electrical Stimulation (tES) in humans to control the disease pathologies prominent in enhancing the synaptic function.

Inhibiting Mitochondrial Cytochrome c Oxidase Downregulates Gene Transcription After Traumatic Brain Injury in Drosophila

Traumatic brain injuries (TBIs) caused by a sudden impact to the head alter behavior and impair physical and cognitive function. Besides the severity, type and area of the brain affected, the outcome of TBI is also influenced by the patient’s biological sex. Previous studies reporting mitochondrial dysfunction mainly focused on exponential reactive oxygen species (ROS) generation, increased mitochondrial membrane potential, and altered mitochondrial dynamics as a key player in the outcome to brain injury. In this study, we evaluated the effect of a near-infrared (NIR) light exposure on gene expression in a Drosophila TBI model. NIR interacts with cytochrome c oxidase (COX) of the electron transport chain to reduce mitochondrial membrane potential hyperpolarization, attenuate ROS generation, and apoptosis. We subjected w¹¹¹⁸ male and female flies to TBI using a high-impact trauma (HIT) device and subsequently exposed the isolated fly brains to a COX-inhibitory wavelength of 750 nm for 2 hours (hr). Genome-wide 3′-mRNA-sequencing of fly brains revealed that injured w¹¹¹⁸ females exhibit greater changes in transcription compared to males at 1, 2, and 4 hours (hr) after TBI. Inhibiting COX by exposure to NIR downregulates gene expression in injured females but has minimal effect in injured males. Our results suggest that mitochondrial COX modulation with NIR alters gene expression in Drosophila following TBI and the response to injury and NIR exposure varies by biological sex.

Advances in the development paradigm of biosample-based biosensors for early ultrasensitive detection of alzheimer's disease

This review highlights current developments, challenges, and future directions for the use of invasive and noninvasive biosample-based small biosensors for early diagnosis of Alzheimer's disease (AD) with biomarkers to incite a conceptual idea from a broad number of readers in this field. We provide the most promising concept about biosensors on the basis of detection scale (from femto to micro) using invasive and noninvasive biosamples such as cerebrospinal fluid (CSF), blood, urine, sweat, and tear. It also summarizes sensor types and detailed analyzing techniques for ultrasensitive detection of multiple target biomarkers (i.e., amyloid beta (Aβ) peptide, tau protein, Acetylcholine (Ach), microRNA137, etc.) of AD in terms of detection ranges and limit of detections (LODs). As the most significant disadvantage of CSF and blood-based detection of AD is associated with the invasiveness of sample collection which limits future strategy with home-based early screening of AD, we extensively reviewed the future trend of new noninvasive detection techniques (such as optical screening and bio-imaging process). To overcome the limitation of non-invasive biosamples with low concentrations of AD biomarkers, current efforts to enhance the sensitivity of biosensors and discover new types of biomarkers using non-invasive body fluids are presented. We also introduced future trends facing an infection point in early diagnosis of AD with simultaneous emergence of addressable innovative technologies.

Diffusion Tensor Imaging Detects Acute Pathology-Specific Changes in the P301L Tauopathy Mouse Model Following Traumatic Brain Injury

Traumatic brain injury (TBI) has been linked with tauopathy. However, imaging methods that can non-invasively detect tau-protein abnormalities following TBI need further investigation. This study aimed to investigate the potential of diffusion tensor imaging (DTI) to detect tauopathy following TBI in P301L mutant-tau-transgenic-pR5-mice. A total of 24 9-month-old pR5 mice were randomly assigned to sham and TBI groups. Controlled cortical injuries/craniotomies were performed for TBI/sham groups followed by DTI data acquisition on days 1 and 7 post-injury. DTI data were analyzed by using voxelwise analysis and track-based spatial statistics for gray matter and white matter. Further, immunohistochemistry was performed for total-tau and phosphorylated-tau, astrocytes, and microglia. To detect the association of DTI with these pathological markers, a correlation analysis was performed between DTI and histology findings. At day 1 post-TBI, DTI revealed a widespread reduction in fractional anisotropy (FA) and axial diffusivity (AxD) in the TBI group compared to shams. On day 7, further reduction in FA, AxD, and mean diffusivity and increased radial diffusivity were observed. FA was significantly increased in the amygdala and cortex. Correlation results showed that in the ipsilateral hemisphere FA reduction was associated with increased phosphorylated-tau and glial-immunoreactivity, whereas in the contralateral regions, the FA increase was associated with increased immunostaining for astrocytes. This study is the first to exploit DTI to investigate the effect of TBI in tau-transgenic mice. We show that alterations in the DTI signal were associated with glial activity following TBI and would most likely reflect changes that co-occur with/without phosphorylated-tau. In addition, FA may be a promising measure to identify discrete pathological processes such as increased astroglia activation, tau-hyperphosphorylation or both in the brain following TBI.

Repetitive Traumatic Brain Injury Causes Neuroinflammation before Tau Pathology in Adolescent P301S Mice

Repetitive closed head injury (rCHI) is commonly encountered in young athletes engaged in contact and collision sports. Traumatic brain injury (TBI) including rCHI has been reported to be an important risk factor for several tauopathies in studies of adult humans and animals. However, the link between rCHI and the progression of tau pathology in adolescents remains to be elucidated. We evaluated whether rCHI can trigger the initial acceleration of pathological tau in adolescent mice and impact the long-term outcomes post-injury. To this end, we subjected adolescent transgenic mice expressing the P301S tau mutation to mild rCHI and assessed tau hyperphosphorylation, tangle formation, markers of neuroinflammation, and behavioral deficits at 40 days post rCHI. We report that rCHI did not accelerate tau pathology and did not worsen behavioral outcomes compared to control mice. However, rCHI induced cortical and hippocampal microgliosis and corpus callosum astrocytosis in P301S mice by 40 days post-injury. In contrast, we did not find significant microgliosis or astrocytosis after rCHI in age-matched WT mice or sham-injured P301S mice. Our data suggest that neuroinflammation precedes the development of Tau pathology in this rCHI model of adolescent repetitive mild TBI.

A roadmap of brain recovery in a mouse model of concussion: insights from neuroimaging

Concussion or mild traumatic brain injury is the most common form of traumatic brain injury with potentially long-term consequences. Current objective diagnosis and treatment options are limited to clinical assessment, cognitive rest, and symptom management, which raises the real danger of concussed patients being released back into activities where subsequent and cumulative injuries may cause disproportionate damages. This study conducted a cross-sectional multi-modal examination investigation of the temporal changes in behavioural and brain changes in a mouse model of concussion using magnetic resonance imaging. Sham and concussed mice were assessed at day 2, day 7, and day 14 post-sham or injury procedures following a single concussion event for motor deficits, psychological symptoms with open field assessment, T2-weighted structural imaging, diffusion tensor imaging (DTI), neurite orientation density dispersion imaging (NODDI), stimulus-evoked and resting-state functional magnetic resonance imaging (fMRI). Overall, a mismatch in the temporal onsets and durations of the behavioural symptoms and structural/functional changes in the brain was seen. Deficits in behaviour persisted until day 7 post-concussion but recovered at day 14 post-concussion. DTI and NODDI changes were most extensive at day 7 and persisted in some regions at day 14 post-concussion. A persistent increase in connectivity was seen at day 2 and day 14 on rsfMRI. Stimulus-invoked fMRI detected increased cortical activation at day 7 and 14 post-concussion. Our results demonstrate the capabilities of advanced MRI in detecting the effects of a single concussive impact in the brain, and highlight a mismatch in the onset and temporal evolution of behaviour, structure, and function after a concussion. These results have significant translational impact in developing methods for the detection of human concussion and the time course of brain recovery.

Serum Amyloid Biomarkers, Tau Protein and YKL-40 Utility in Detection, Differential Diagnosing, and Monitoring of Dementia

Introduction: The diagnosis and treatment of dementia is one of the greatest challenges in contemporary health care. The widespread use of dementia biomarkers would improve the quality of life of patients and reduce the economic costs of the disease. The aim of the study was to evaluate the usefulness of proteins related to the Alzheimer's disease pathogenesis-amyloid beta isoform (Aβ) and total tau protein (t-tau), as well as the quite recently discovered marker YKL-40 in the most common types of dementia. Methods: 60 dementia (AD-Alzheimer's disease, VaD-vascular dementia, MxD-mixed dementia) and 20 cognitively normal subjects over 60 years old were examined. Subjects with dementia of etiology different than AD or VaD and with neoplastic or chronic inflammatory diseases were excluded. Concentrations of Aβ40, Aβ42, t-tau, and YKL-40 were measured in serum using ELISA kits on admission and after 4 weeks of inpatient treatment. ANOVA and Tukey's test or Dunn's test were used to perform comparison tests between groups. Correlations were measured using Pearson's coefficient. Biomarker diagnostic utility was assessed with ROC analysis. Results: YKL-40 differentiates between cognitively normal and mild dementia patients with 85% sensitivity and specificity and t-tau with 72% sensitivity and 70% specificity. YKL-40 and t-tau concentrations correlate with each other and with the severity of clinically observed cognitive decline. Conclusions: YKL-40 is a sensitive and specific biomarker of early dementia and, to a lesser extent, of dementia progression, however, many comorbidities may influence its levels. In such conditions, less specific but still reliable t-tau may serve as an alternative marker. Obtained results did not confirm the diagnostic utility of amyloid biomarkers.

Alternative splicing in aging and Alzheimer's disease: Highlighting the role of tau and estrogen receptor α isoforms in the hypothalamus

Human genes show the highest efficacy of alternative splicing (AS) in the brain as compared to other tissues. Within the brain, a remarkably rich diversity of AS events was identified in the hypothalamus. The AS frequency is increased in the aging brain. Such AS events, as intron retention and accumulation of circular RNAs, were acknowledged as some of the main hallmarks of the aging brain. In Alzheimer's disease (AD) pivotal (tau gene, in particular), risk, candidate and other genes show significant alterations in AS. Therefore AD has been suggested to be a disease of dysregulated AS. One of the reported risk factors for AD is estrogen deficiency that may interfere with the extension of neurobrillary tangles. Mounting evidence suggests that estrogens may decrease hyperphosphorylated tau deposition in the brain. Furthermore, AS of estrogen receptor α (ERα) mRNA is decreased in AD brain areas with the highest tau load. These potential interactions among tau, estrogens, and ERα AS may be important for the development of therapeutic and preventive strategies for AD. The intriguing point is that the amount of splice variants of ERα in the hypothalamus and the hippocampus is increased in aging and decreased in AD, while ERα is one of the regulators of AS and is subject to AS itself.

The Microbiota-Gut-Brain Axis and Alzheimer's Disease: Neuroinflammation Is to Blame?

For years, it has been reported that Alzheimer’s disease (AD) is the most common cause of dementia. Various external and internal factors may contribute to the early onset of AD. This review highlights a contribution of the disturbances in the microbiota–gut–brain (MGB) axis to the development of AD. Alteration in the gut microbiota composition is determined by increase in the permeability of the gut barrier and immune cell activation, leading to impairment in the blood–brain barrier function that promotes neuroinflammation, neuronal loss, neural injury, and ultimately AD. Numerous studies have shown that the gut microbiota plays a crucial role in brain function and changes in the behavior of individuals and the formation of bacterial amyloids. Lipopolysaccharides and bacterial amyloids synthesized by the gut microbiota can trigger the immune cells residing in the brain and can activate the immune response leading to neuroinflammation. Growing experimental and clinical data indicate the prominent role of gut dysbiosis and microbiota–host interactions in AD. Modulation of the gut microbiota with antibiotics or probiotic supplementation may create new preventive and therapeutic options in AD. Accumulating evidences affirm that research on MGB involvement in AD is necessary for new treatment targets and therapies for AD.