Neuron-Derived Exosome Proteins May Contribute to Progression From Repetitive Mild Traumatic Brain Injuries to Chronic Traumatic Encephalopathy

Identification of differentially expressed exosome proteins in serum as potential biomarkers for cognitive impairments in cerebral small vessel disease

BACKGROUND

Cognitive impairment arising from cerebral small vessel disease (CSVD) represents a critical subtype of vascular cognitive impairments (VCI) and is the primary cause of vascular dementia. However, identifying reliable clinical and laboratory indicators for this disease remain elusive. We hypothesize that plasma exosome proteins hold the potential to serve as biomarkers for the onset of cognitive dysfunction associated with cerebrovascular diseases.

METHODS

We employed TMT-based proteomics to discern variations in serum exosome proteomes between individuals with cognitive impairments due to CSVD and healthy volunteers.

RESULTS

Each group comprised 18 subjects, and through differential expression analysis, we identified 22 down-regulated and 8 up-regulated proteins between the two groups. Our research revealed 30 differentially expressed plasma exosome proteins, including histone, proteasome, clusterin and coagulation factor XIII, in individuals with cognitive impairments caused by CSVD.

CONCLUSION

The 30 differentially expressed plasma exosome proteins identified in our study are promising as biomarkers for diagnosing cognitive impairments resulting from CSVD. These findings may help us better understand the underlying pathological mechanisms involved in the diseases.

Exploring the Potential of Exosomal Biomarkers in Mild Traumatic Brain Injury and Post-Concussion Syndrome: A Systematic Review

BACKGROUND

Alongside their long-term effects, post-concussion syndrome (PCS) and mild traumatic brain injuries (mTBI) are significant public health concerns. Currently, there is a lack of reliable biomarkers for diagnosing and monitoring mTBI and PCS. Exosomes are small extracellular vesicles secreted by cells that have recently emerged as a potential source of biomarkers for mTBI and PCS due to their ability to cross the blood-brain barrier and reflect the pathophysiology of brain injury. In this study, we aimed to investigate the role of salivary exosomal biomarkers in mTBI and PCS.

METHODS

A systematic review using the PRISMA guidelines was conducted, and studies were selected based on their relevance to the topic.

RESULTS

The analyzed studies have shown that exosomal tau, phosphorylated tau (p-tau), amyloid beta (Aβ), and microRNAs (miRNAs) are potential biomarkers for mTBI and PCS. Specifically, elevated levels of exosomal tau and p-tau have been associated with mTBI and PCS as well as repetitive mTBI. Dysregulated exosomal miRNAs have also been observed in individuals with mTBI and PCS. Additionally, exosomal Prion cellular protein (PRPc), coagulation factor XIII (XIIIa), synaptogyrin-3, IL-6, and aquaporins have been identified as promising biomarkers for mTBI and PCS.

CONCLUSION

Salivary exosomal biomarkers have the potential to serve as non-invasive and easily accessible diagnostic and prognostic tools for mTBI and PCS. Further studies are needed to validate these biomarkers and develop standardized protocols for their use in clinical settings. Salivary exosomal biomarkers can improve the diagnosis, monitoring, and treatment of mTBI and PCS, leading to improved patient outcomes.

Intrinsic factors behind long-COVID: I. Prevalence of the extracellular vesicles

It can be argued that the severity of COVID-19 has decreased in many countries. This could be a result of the broad coverage of the population by vaccination campaigns, which often reached an almost compulsory status in many places. Furthermore, significant roles were played by the multiple mutations in the body of the virus, which led to the emergence of several new SARS-CoV-2 variants with enhanced infectivity but dramatically reduced pathogenicity. However, the challenges associated with the development of various side effects and their persistence for long periods exceeding 20 months as a result of the SARS-CoV-2 infection, or taking available vaccines against it, are spreading horizontally and vertically in number and repercussions. For example, the World Health Organization announced that there are more than 17 million registered cases of long-COVID (also known as post-COVID syndrome) in the European Union countries alone. Furthermore, by using the PubMed search engine, one can find that more than 10 000 articles have been published focusing exclusively on long-COVID. In light of these enormous and ever-increasing numbers of cases and published articles, most of which are descriptive of the various long-COVID symptoms, the need to know the reasons behind this phenomenon raises several important questions. Is long-COVID caused by the continued presence of the virus or one/several of its components in the recovering individual body for long periods of time, which urges the body to respond in a way that leads to long-COVID development? Or are there some latent and limited reasons related to the recovering patients themselves? Or is it a sum of both? Many observations support a positive answer to the first question, whereas others back the second question but typically without releasing a fundamental reason/signal behind it. Whatever the answer is, it seems that the real reasons behind this widespread phenomenon remain unclear. This report opens a series of articles, in which we will try to shed light on the underlying causes that could be behind the long-COVID phenomenon.

Exosome: The “Off-the-Shelf” Cellular Nanocomponent as a Potential Pathogenic Agent, a Disease Biomarker, and Neurotherapeutics

Exosomes are nanosized “off-the-shelf” lipid vesicles released by almost all cell types and play a significant role in cell–cell communication. Exosomes have already been proven to carry cell-specific cargos of proteins, lipids, miRNA, and noncoding RNA (ribonucleic acid). These vesicles can be selectively taken up by the neighboring cell and can regulate cellular functions. Herein, we have discussed three different roles of exosomes in neuroscience. First, we have discussed how exosomes play the role of a pathogenic agent as a part of cell–cell communication and transmit pathogens such as amyloid-beta (Aβ), further helping in the propagation of neurodegenerative and other neurological diseases. In the next section, the review talks about the role of exosomes in biomarker discovery in neurological disorders. Toward the end, we have reviewed how exosomes can be harnessed and engineered for therapeutic purposes in different brain diseases. This review is based on the current knowledge generated in this field and our comprehension of this domain.

SARS-CoV-2 and mitochondrial proteins in neural-derived exosomes of COVID-19

Objective

As SARS‐CoV‐2 is known to invade neural cell mitochondria, a plasma system for quantifying central nervous system proteins in living humans was used to investigate neuropathogenic mechanisms of long‐COVID‐19.

Methods

SARS‐CoV‐2 proteins and mitochondrial proteins (MPs) in enriched plasma neuron‐derived extracellular vesicles (NDEVs) and astrocyte‐derived EVs (ADEVs) were quantified in resolved acute COVID‐19 without post‐acute sequelae of SARS‐CoV‐2 (PASC), PASC without neuropsychiatric manifestations (NP), PASC with NP and healthy controls.

Results

NDEV and ADEV mean levels of SARS‐CoV‐2 S1 and nucleocapsid (N) proteins were higher in all PASC sub‐groups than controls, but only N levels were higher in PASC with than without NP. Exosome marker CD81‐normalized NDEV mean levels of subunit 6 of MP respiratory chain complex I and subunit 10 of complex III, and neuroprotective MPs Humanin and mitochondrial open‐reading frame of the 12S rRNA‐c (MOTS‐c) all were decreased significantly in PASC with NP but not in PASC without NP relative to controls. NDEV levels of MPs voltage‐dependent anion‐selective channel protein 1 (VDAC1) and N‐methyl‐D‐aspartate receptor 1 (NMDAR1) were decreased in PASC without and with NP, whereas those of calcium channel MPs mitochondrial calcium uniporter (MCU), sodium/calcium exchanger (NCLX) and leucine zipper EF‐hand containing transmembrane 1 protein (LETM1) were decreased only in PASC with NP. ADEV levels of MCU and NCLX only were increased in PASC without and with NP.

Interpretation

Abnormal NDEV and ADEV levels of SARS‐CoV‐2 N and S1 protein and MPs correlate with NP and may be biomarkers for long‐COVID prognostics and therapeutic trials. ANN NEUROL 2022;91:772–781

Efficacy of stem cell secretome in the treatment of traumatic brain injury: A systematic review and meta-analysis of preclinical studies

Traumatic brain injury (TBI) remains a public health challenge and represents one of the major contributors to disability and mortality worldwide among all trauma-related injuries. This study aimed to determine a precise effect size of secretome intervention in TBI. We performed a systematic literature search through Cochrane, MEDLINE Complete, PubMed and Scopus databases for articles published until June 2021. The search terms used include cells OR stem cells OR mesenchymal stem cells AND secretome OR conditioned medium OR extracellular vesicles OR exosomes OR microvesicles AND traumatic brain injury OR head injury. Neurological deficits and neuroinflammation were the outcome measures assessed after the intervention. Thirty-one (31) studies involving mouse, rat and swine were enrolled for the meta-analysis. Secretome significantly improved structural and functional recovery when compared with control. The mean effect sizes were as follows: modified neurological severity score (mNSS) (-2.65, 95% CI: -3.42, -1.87, p < 0.00001), impact size (-3.02 mm³, 95% CI: -4.97, -1.08, p = 0.002) and latency to platform (-17.20 s, 95% CI: -23.91, -10.50, p < 0.00001). Similarly, intervention with secretome reduced neuroinflammation after TBI. The results of meta-regression showed that the source of secretome, TBI models and duration of follow-up did not influence the mNSS. Furthermore, the methodological quality of the studies was moderate as shown by the risk of bias assessment. Publication bias was observed for the mNSS. This meta-analysis provides preclinical evidence of secretome intervention in TBI, suggesting that it can be explored as a therapeutic agent for TBI and other neurological disorders in humans.

Inhibition of Exosome Release Alleviates Cognitive Impairment After Repetitive Mild Traumatic Brain Injury

Background

Repetitive mild traumatic brain injury (rmTBI) is closely associated with chronic traumatic encephalopathy (CTE). Neuroinflammation and neuropathological protein accumulation are key links to CTE progression. Exosomes play important roles in neuroinflammation and neuropathological protein accumulation and spread. Here, we explored the role of brain-derived exosomes (BDEs) in mice with rmTBI and how the inhibition of BDE release contributes to neuroprotection.

Methods

GW4869 was used to inhibit exosome release, and behavioural tests, PET/CT and western blotting were conducted to explore the impact of this inhibition from different perspectives. We further evaluated cytokine expression by Luminex and microglial activation by immunofluorescence in mice with rmTBI after exosome release inhibition.

Results

Inhibition of BDE release reversed cognitive impairment in mice with rmTBI, enhanced glucose uptake and decreased neuropathological protein expression. Inhibition of BDE release also changed cytokine production trends and enhanced microglial proliferation.

Conclusion

In this study, we found that BDEs are key factor in cognitive impairment in mice with rmTBI and that microglia are the main target of BDEs. Thus, inhibition of exosome release may be a new strategy for improving CTE prognoses.

Rab35 and glucocorticoids regulate APP and BACE1 trafficking to modulate Aβ production

Chronic stress and elevated glucocorticoids (GCs), the major stress hormones, are risk factors for Alzheimer’s disease (AD) and promote AD pathomechanisms, including overproduction of toxic amyloid-β (Aβ) peptides and intraneuronal accumulation of hyperphosphorylated Tau protein. The latter is linked to downregulation of the small GTPase Rab35, which mediates Tau degradation via the endolysosomal pathway. Whether Rab35 is also involved in Aβ overproduction remains an open question. Here, we find that hippocampal Rab35 levels are decreased not only by stress/GC but also by aging, another AD risk factor. Moreover, we show that Rab35 negatively regulates Aβ production by sorting amyloid precursor protein (APP) and β-secretase (BACE1) out of the endosomal network, where they interact to produce Aβ. Interestingly, Rab35 coordinates distinct intracellular trafficking steps for BACE1 and APP, mediated by its effectors OCRL and ACAP2, respectively. Finally, we demonstrate that Rab35 overexpression prevents the amyloidogenic trafficking of APP and BACE1 induced by high GC levels. These studies identify Rab35 as a key regulator of APP processing and suggest that its downregulation may contribute to stress-related and AD-related amyloidogenesis.

A comprehensive study to delineate the role of an extracellular vesicle-associated microRNA-29a in chronic methamphetamine use disorder

Extracellular vesicles (EVs), which express a repertoire of cargo molecules (cf. proteins, microRNA, lipids, etc.), have been garnering a prominent role in the modulation of several cellular processes. Here, using both non-human primate and rodent model systems, we provide evidence that brain-derived EV (BDE) miRNA, miR-29a-3p (mir-29a), is significantly increased during chronic methamphetamine (MA) exposure. Further, miR-29a levels show significant increase both with drug-seeking and reinstatement in a rat MA self-administration model. We also show that EV-associated miR-29a is enriched in EV pool comprising of small EVs and exomeres and further plays a critical role in MA-induced inflammation and synaptodendritic damage. Furthermore, treatment with the anti-inflammatory drug ibudilast (AV411), which is known to reduce MA relapse, decreased the expression of miR-29a and subsequently attenuated inflammation and rescued synaptodendritic injury. Finally, using plasma from MUD subjects, we provide translational evidence that EV-miR29a could potentially serve as a biomarker to detect neuronal damage in humans diagnosed with MA use disorder (MUD). In summary, our work suggests that EV-associated miR-29a-3p plays a crucial role in MUD and might be used as a potential blood-based biomarker for detecting chronic inflammation and synaptic damage.

Shotgun-based proteomics of extracellular vesicles in Alzheimer's disease reveals biomarkers involved in immunological and coagulation pathways

Alzheimer's disease (AD) is the most common form of dementia and without readily available clinical biomarkers. Blood-derived proteins are routinely used for diagnostics; however, comprehensive plasma profiling is challenging due to the dynamic range in protein concentrations. Extracellular vesicles (EVs) can cross the blood-brain barrier and may provide a source for AD biomarkers. We investigated plasma-derived EV proteins for AD biomarkers from 10 AD patients, 10 Mild Cognitive Impairment (MCI) patients, and 9 healthy controls (Con) using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The ultracentrifuged EVs were washed and confirmed according to the MISEV2018 guidelines. Some AD patients presented with highly elevated FXIIIA1 (log₂ FC: 4.6, p-value: 0.005) and FXIIIB (log₂ FC: 4.9, p-value: 0.018). A panel of proteins was identified discriminating Con from AD (AUC: 0.91, CI: 0.67-1.00) with ORM2 (AUC: 1.00, CI: 1.00-1.00), RBP4 (AUC: 0.99, CI: 0.95-1.00), and HYDIN (AUC: 0.89, CI: 0.72-1.00) were found especially relevant for AD. This indicates that EVs provide an easily accessible matrix for possible AD biomarkers. Some of the MCI patients, with similar protein profiles as the AD group, progressed to AD within a 2-year timespan.

Developing methods to detect and diagnose chronic traumatic encephalopathy during life: rationale, design, and methodology for the DIAGNOSE CTE Research Project

BACKGROUND

Chronic traumatic encephalopathy (CTE) is a neurodegenerative disease that has been neuropathologically diagnosed in brain donors exposed to repetitive head impacts, including boxers and American football, soccer, ice hockey, and rugby players. CTE cannot yet be diagnosed during life. In December 2015, the National Institute of Neurological Disorders and Stroke awarded a seven-year grant (U01NS093334) to fund the "Diagnostics, Imaging, and Genetics Network for the Objective Study and Evaluation of Chronic Traumatic Encephalopathy (DIAGNOSE CTE) Research Project." The objectives of this multicenter project are to: develop in vivo fluid and neuroimaging biomarkers for CTE; characterize its clinical presentation; refine and validate clinical research diagnostic criteria (i.e., traumatic encephalopathy syndrome [TES]); examine repetitive head impact exposure, genetic, and other risk factors; and provide shared resources of anonymized data and biological samples to the research community. In this paper, we provide a detailed overview of the rationale, design, and methods for the DIAGNOSE CTE Research Project.

METHODS

The targeted sample and sample size was 240 male participants, ages 45-74, including 120 former professional football players, 60 former collegiate football players, and 60 asymptomatic participants without a history of head trauma or participation in organized contact sports. Participants were evaluated at one of four U.S. sites and underwent the following baseline procedures: neurological and neuropsychological examinations; tau and amyloid positron emission tomography; magnetic resonance imaging and spectroscopy; lumbar puncture; blood and saliva collection; and standardized self-report measures of neuropsychiatric, cognitive, and daily functioning. Study partners completed similar informant-report measures. Follow-up evaluations were intended to be in-person and at 3 years post-baseline. Multidisciplinary diagnostic consensus conferences are held, and the reliability and validity of TES diagnostic criteria are examined.

RESULTS

Participant enrollment and all baseline evaluations were completed in February 2020. Three-year follow-up evaluations began in October 2019. However, in-person evaluation ceased with the COVID-19 pandemic, and resumed as remote, 4-year follow-up evaluations (including telephone-, online-, and videoconference-based cognitive, neuropsychiatric, and neurologic examinations, as well as in-home blood draw) in February 2021.

CONCLUSIONS

Findings from the DIAGNOSE CTE Research Project should facilitate detection and diagnosis of CTE during life, and thereby accelerate research on risk factors, mechanisms, epidemiology, treatment, and prevention of CTE.

TRIAL REGISTRATION

NCT02798185.

Combined bioscaffold with stem cells and exosomes can improve traumatic brain injury

The intricacy of the brain, along with the existence of blood brain barrier (BBB) does complicate the delivery of effective therapeutics through simple intravascular injection. Hence, an effective delivery mechanism of therapeutics in the event of either traumatic brain injury (TBI) or other brain injuries is needed. Stem cells can promote regeneration and repair injury. The usage of biomaterials and exosomes in transporting stem cells to target lesion sites has been suggested as a potential option. The combination of biomaterials with modified exosomes can help in transporting stem cells to injury sites, whiles also increasing their survival and promoting effective treatment. Herein, we review the current researches pertinent to biological scaffolds and exosomes in repairing TBI and present the current progress and new direction in the clinical setting. We begin with the role of bioscaffold in treating neuronal conditions, the effect of exosomes in injury, and conclude with the improvement of TBI via the employment of combined exosomes, bioscaffold and stem cells.

Extracellular Vesicles as an Emerging Frontier in Spinal Cord Injury Pathobiology and Therapy

Extracellular vesicles (EVs) are membrane-delimited particles that are secreted by nearly all cell types. EVs mediate crucial physiological functions and pathophysiological processes in the CNS. As carriers of diverse bioactive cargoes (e.g., proteins, lipids, and nucleic acids) that can be modified in response to external stimuli, EVs have emerged as pathological mediators following neurotrauma such as spinal cord injury (SCI). We discuss the roles of endogenous EVs in the CNS as well as crosstalk with peripheral EVs in relation to neurotrauma, with a particular focus on SCI. We then summarize the status of EV-based therapeutic advances in preclinical animal models for these conditions. Finally, we discuss new bioengineering strategies that are poised to enhance CNS-specific therapeutic capabilities of EVs.

Characterization and Biomarker Analyses of Post-COVID-19 Complications and Neurological Manifestations

As the SARS-CoV-2 pandemic continues, reports have demonstrated neurologic sequelae following COVID-19 recovery. Mechanisms to explain long-term neurological sequelae are unknown and need to be identified. Plasma from 24 individuals recovering from COVID-19 at 1 to 3 months after initial infection were collected for cytokine and antibody levels and neuronal-enriched extracellular vesicle (nEV) protein cargo analyses. Plasma cytokine IL-4 was increased in all COVID-19 participants. Volunteers with self-reported neurological problems (nCoV, n = 8) had a positive correlation of IL6 with age or severity of the sequalae, at least one co-morbidity and increased SARS-CoV-2 antibody compared to those COVID-19 individuals without neurological issues (CoV, n = 16). Protein markers of neuronal dysfunction including amyloid beta, neurofilament light, neurogranin, total tau, and p-T181-tau were all significantly increased in the nEVs of all participants recovering from COVID-19 compared to historic controls. This study suggests ongoing peripheral and neuroinflammation after COVID-19 infection that may influence neurological sequelae by altering nEV proteins. Individuals recovering from COVID-19 may have occult neural damage while those with demonstrative neurological symptoms additionally had more severe infection. Longitudinal studies to monitor plasma biomarkers and nEV cargo are warranted to assess persistent neurodegeneration and systemic effects.

MiR-126-3p-Enriched Extracellular Vesicles from Hypoxia-Preconditioned VSC 4.1 Neurons Attenuate Ischaemia-Reperfusion-Induced Pain Hypersensitivity by Regulating the PIK3R2-Mediated Pathway

Recent evidence suggests that hypoxia preconditioning can alter the microRNA (miRNA) profile of extracellular vesicles (EVs) and has better neuroprotective effects when enriched miRs are delivered to recipients. However, the roles of exosomal miRNAs in regulating ischaemia-reperfusion (IR)-induced pain hypersensitivity are largely unknown. Thus, we isolated EVs from normoxia-conditioned neurons (Nor-VSC EVs) and Hypo-VSC EVs by ultracentrifugation. After the initial screening by a microarray analysis and quantitative RT-PCR (qRT-PCR), miR-126-3p, which was detected as the most altered miR in the Hypo-VSC EVs, was further confirmed by applying GW4869 to inhibit exosomal secretion. Moreover, transfection with a miR-126 mimic obviously increased miR-126-3p expression in Nor-VSC EVs, whereas a miR-126 inhibitor prevented the increase in miR-126-3p in Hypo-VSC EVs. A rat model of pain was established by performing 8-min occlusion of the aorta. Following IR, compared with the Nor-VSC EVs- or antagomir-126-injected rats, the Hypo-VSC EVs-injected rats displayed improved pain hypersensitivity demonstrated as higher PWT and PWL values. Mechanistically, PIK3R2 is a target of miR-126-3p and might be a modulator of the phosphoinositide 3-kinase (PI3K)/Akt pathway as the PIK3R2 and PI3K immunoreactivities in each group were changed in opposite directions. Compared with the controls, higher protein levels of PI3K and phosphorylated Akt but lower levels of phosphorylated nuclear factor-κ B (NF-κB), tumour necrosis factor (TNF)-α and interleukin (IL)-1β were detected in the spinal cords of the Hypo-VSC EVs-injected rats, and these effects were impaired by an injection of Hypo-VSC EVs combined with antagomir-126. Collectively, the miR-126-3p-enriched Hypo-VSC EVs attenuated IR-induced pain hypersensitivity by restoring miR-126-3p expression in the injured spinal cord and subsequently modulating PIK3R2-mediated PI3K/Akt and NF-κB signalling pathways.

Neuroimaging and advanced research techniques may lead to improved outcomes in military members suffering from traumatic brain injury

Recent military conflicts in Iraq and Afghanistan have resulted in the significant increase in blast-related traumatic brain injury (TBI), leading to increased Department of Defense interest in its potential long-term effects ranging from the mildest head injuries termed subconcussive trauma to the most debilitating termed chronic traumatic encephalopathy (CTE). Most patients with mild TBI will recover quickly while others report persistent symptoms called postconcussive syndrome. Repeated concussive and subconcussive head injuries result in neurodegenerative conditions that may hinder the injured for years. Fundamental questions about the nature of these injuries and recovery remain unanswered. Clinically, patients with CTE present with either affective changes or cognitive impairment. Genetically, there have been no clear risk factors identified. The discovery that microglia of the cerebral cortex discharged small extracellular vesicles in the injured and adjacent regions to a TBI may soon shed light on the immediate impact injury mechanisms. The combination of neuroimaging and advanced research techniques may, one day, fill critical knowledge gaps and lead to significant TBI research and treatment advancements.

Exploring brain insulin resistance in adults with bipolar depression using extracellular vesicles of neuronal origin

Accumulating evidence suggests that disrupted insulin signaling is involved in bipolar disorder (BD) pathogenesis. Herein, we aimed to directly explore the potential role of neuronal insulin signaling using an innovative technique based on biomarkers derived from plasma extracellular vesicles enriched for neuronal origin (NEVs). We leveraged plasma samples from a randomized, double-blind, placebo-controlled, 12-week clinical trial evaluating infliximab as a treatment of bipolar depression. We isolated NEVs using immunoprecipitation against neuronal marker L1CAM from samples collected at baseline and weeks 2, 6 and 12 (endpoint) and measured NEV biomarkers using immunoassays. We assessed neuronal insulin signaling at its first node (IRS-1) and along the canonical (Akt, GSK-3β, p70S6K) and alternative (ERK1/2, JNK and p38-MAPK) pathways. A subset of participants (n = 27) also underwent whole-brain magnetic resonance imaging (MRI) at baseline and endpoint. Pre-treatment, NEV biomarkers of insulin signaling were independently associated with cognitive function and MRI measures (i.e. hippocampal and ventromedial prefrontal cortex [vmPFC] volumes). In fact, the association between IRS-1 phosphorylation at serine site 312 (pS312-IRS-1), an indicator of insulin resistance, and cognitive dysfunction was mediated by vmPFC volume. In the longitudinal analysis, patients treated with infliximab, a tumor necrosis factor-alpha antagonist with known insulin sensitizing properties, compared to those treated with placebo, had augmented phosphorylation of proteins from the alternative pathway. Infliximab responders had significant increases in phosphorylated JNK levels, relative to infliximab non-responders and placebo responders. In addition, treatment with infliximab resulted in increase in MRI measures of brain volume; treatment-related changes in the dorsolateral prefrontal cortex volume were mediated by changes in biomarkers from the insulin alternative pathway. In conclusion, our findings support the idea that brain insulin signaling is a target for further mechanistic and therapeutic investigations.

Neurofilament light chain level in plasma extracellular vesicles and Parkinson's disease

BACKGROUND

Neurofilament light chain (NfL) is essential for axonal maintenance and reflects neuronal damage. Extracellular vesicles (EVs), especially exosomes, secreted by cells into the blood, are emerging as novel biomedical research platforms of physiological and pathological processes. The present study investigated the possible association between plasma EV NfL and Parkinson's disease (PD).

METHODS

One hundred and sixteen patients with mild to moderate PD and 46 non-PD, neurological controls were recruited, and their clinical motor symptoms and cognitive function were evaluated. Plasma EVs were isolated using an exoEasy kit, and immunomagnetic reduction assay was used to assess EV NfL level. Statistical analysis was performed using SPSS 25.0, and p < 0.05 was considered significant.

RESULTS

The isolated plasma EVs were validated according to size and the presence of specific surface markers. Compared with the neurological control group, the levels of plasma EV NfL in patients with PD were not significantly different (PD: 9.42 ± 3.89, control: 9.53 ± 3.62 pg/mL plasma, p = 0.71). On the other hand, plasma EV NfL in patients with PD trendwise correlated with the severity of akinetic rigidity (p = 0.05). PD patients with optimal EV NfL (lowest quartile) had 6.66 ± 2.08 lower Unified Parkinson's Disease Rating Scale-III score after adjustment for age, sex, and disease duration.

CONCLUSION

Plasma EV NfL levels did not distinguish patients with PD from the neurological control group. The possible correlation between plasma EV NfL with the severity of motor symptoms within the PD patients, especially with akinetic rigidity, was noted. Further clinical validation of the blood EV NfL by a longitudinal follow-up study of PD patients is warranted.

Altered Insulin Receptor Substrate 1 Phosphorylation in Blood Neuron-Derived Extracellular Vesicles From Patients With Parkinson's Disease

INTRODUCTION

Diabetes increases the risk of Parkinson's disease (PD). The phosphorylation of type 1 insulin receptor substrate (IRS-1) determines the function of insulin signaling pathway. Extracellular vesicles (EVs) are emerging as biomarkers of human diseases. The present study investigated whether PD patients exert altered phosphorylation IRS-1 (p-IRS-1) inside the blood neuron-derived extracellular vesicles (NDEVs).

RESEARCH DESIGN AND METHODS

In total, there were 94 patients with PD and 63 healthy controls recruited and their clinical manifestations were evaluated. Blood NDEVs were isolated using the immunoprecipitation method, and Western blot analysis was conducted to assess total IRS-1, p-IRS-1, and downstream substrates level in blood NDEVs. Statistical analysis was performed using SPSS 19.0, and p < 0.05 was considered significant.

RESULTS

The isolated blood EVs were validated according to the presence of CD63 and HSP70, nanoparticle tracking analysis and transmission electron microscopy. NDEVs were positive with neuronal markers. PD patients exerted significantly higher level of p-IRS-1S312 in blood NDEVs than controls. In addition, the p-IRS-1S312 levels in blood NDEVs was positively associated with the severity of tremor in PD patients after adjusting of age, sex, hemoglobin A1c, and body mass index (BMI).

CONCLUSION

PD patients exerted altered p-IRS-1S312 in the blood NDEVs, and also correlated with the severity of tremor. These findings suggested the association between dysfunctional insulin signaling pathway with PD. The role of altered p-IRS-1S312 in blood NDEVs as a segregating biomarker of PD required further cohort study to assess the association with the progression of PD.

Advancing medicine for Alzheimer's disease: A plasma neural exosome platform

Enrichment of neurally derived extracellular vesicles of several cell-types from plasma for protein quantification longitudinally in living patients with Alzheimer's disease has permitted the development of a tentative temporal framework of initiating events, progression mechanisms, and amplification processes. Interactions of beta-amyloid peptides with an elevated level of their normal prion protein dendritic receptor and of phospho-tau species with their synaptogyrin-3 synaptic vesicle receptor replace excessive production and accumulation of neuropathic proteins as the major initiating events. Synaptic dysfunction and microvascular angiopathy are confirmed as early progression mechanisms of decreased neuronal network connectivity, hypoxia, altered blood-brain barrier, and neurocellular degeneration. Neurally derived extracellular vesicle protein abnormalities also reveal a range of later amplification processes that encompasses insulin resistance, lysosomal defects, decreased survival factors, increased reactive oxygen species, and excessive neuroinflammation. New potential therapeutic targets also are suggested as well as the likely timing of their pathogenic engagement.

Assessment of Long-Term Effects of Sports-Related Concussions: Biological Mechanisms and Exosomal Biomarkers

Concussion or mild traumatic brain injury (mTBI) in athletes can cause persistent symptoms, known as post-concussion syndrome (PCS), and repeated injuries may increase the long-term risk for an athlete to develop neurodegenerative diseases such as chronic traumatic encephalopathy (CTE), and Alzheimer's disease (AD). The Center for Disease Control estimates that up to 3.8 million sport-related mTBI are reported each year in the United States. Despite the magnitude of the phenomenon, there is a current lack of comprehensive prognostic indicators and research has shown that available monitoring tools are moderately sensitive to short-term concussion effects but less sensitive to long-term consequences. The overall aim of this review is to discuss novel, quantitative, and objective measurements that can predict long-term outcomes following repeated sports-related mTBIs. The specific objectives were (1) to provide an overview of the current clinical and biomechanical tools available to health practitioners to ensure recovery after mTBIs, (2) to synthesize potential biological mechanisms in animal models underlying the long-term adverse consequences of mTBIs, (3) to discuss the possible link between repeated mTBI and neurodegenerative diseases, and (4) to discuss the current knowledge about fluid biomarkers for mTBIs with a focus on novel exosomal biomarkers. The conclusions from this review are that current post-concussion clinical tests are not sufficiently sensitive to injury and do not accurately quantify post-concussion alterations associated with repeated mTBIs. In the current review, it is proposed that current practices should be amended to include a repeated symptom inventory, a cognitive assessment of executive function and impulse control, an instrumented assessment of balance, vestibulo-ocular assessments, and an improved panel of blood or exosome biomarkers.

Extracellular Vesicle Proteins and MicroRNAs as Biomarkers for Traumatic Brain Injury

Traumatic brain injury (TBI) is a heterogeneous condition, associated with diverse etiologies, clinical presentations and degrees of severity, and may result in chronic neurobehavioral sequelae. The field of TBI biomarkers is rapidly evolving to address the many facets of TBI pathology and improve its clinical management. Recent years have witnessed a marked increase in the number of publications and interest in the role of extracellular vesicles (EVs), which include exosomes, cell signaling, immune responses, and as biomarkers in a number of pathologies. Exosomes have a well-defined lipid bilayer with surface markers that reflect the cell of origin and an aqueous core that contains a variety of biological material including proteins (e.g., cytokines and growth factors) and nucleic acids (e.g., microRNAs). The presence of proteins associated with neurodegenerative changes such as amyloid-β, α-synuclein and phosphorylated tau in exosomes suggests a role in the initiation and propagation of neurological diseases. However, mechanisms of cell communication involving exosomes in the brain and their role in TBI pathology are poorly understood. Exosomes are promising TBI biomarkers as they can cross the blood-brain barrier and can be isolated from peripheral fluids, including serum, saliva, sweat, and urine. Exosomal content is protected from enzymatic degradation by exosome membranes and reflects the internal environment of their cell of origin, offering insights into tissue-specific pathological processes. Challenges in the clinical use of exosomal cargo as biomarkers include difficulty in isolating pure exosomes, variable yields of the isolation processes, quantification of vesicles, and lack of specificity of exosomal markers. Moreover, there is no consensus regarding nomenclature and characteristics of EV subtypes. In this review, we discuss current technical limitations and challenges of using exosomes and other EVs as blood-based biomarkers, highlighting their potential as diagnostic and prognostic tools in TBI.

Extracellular Vesicle Biomarkers Reveal Inhibition of Neuroinflammation by Infliximab in Association with Antidepressant Response in Adults with Bipolar Depression

Accumulating evidence suggests that neuroinflammation is involved in bipolar disorder (BD) pathogenesis. The tumor necrosis factor-alpha (TNF-α) antagonist infliximab was recently reported to improve depressive symptoms in a subpopulation of individuals with BD and history of childhood maltreatment. To explore the mechanistic mediators of infliximab's effects, we investigated its engagement with biomarkers of cellular response to inflammation derived from plasma extracellular vesicles enriched for neuronal origin (NEVs). We hypothesized that infliximab, compared to placebo, would decrease TNF-α receptors (TNFRs) and nuclear factor-kappa B (NF-κB) pathway signaling biomarkers, and that history of childhood abuse would moderate infliximab's effects. We immunocaptured NEVs from plasma samples collected at baseline and at weeks 2, 6, and 12 (endpoint) from 55 participants of this clinical trial and measured NEV biomarkers using immunoassays. A subset of participants (n = 27) also underwent whole-brain magnetic resonance imaging at baseline and endpoint. Childhood physical abuse moderated treatment by time interactions for TNFR1 (χ² = 9.275, p = 0.026), NF-κB (χ² = 13.825, p = 0.003), and inhibitor of NF-κB (IκBα) (χ² = 7.990, p = 0.046), indicating that higher levels of physical abuse were associated with larger biomarker decreases over time. Moreover, the antidepressant response to infliximab was moderated by TNFR1 (χ² = 7.997, p = 0.046). In infliximab-treated participants, reductions in TNFR1 levels were associated with improvement of depressive symptoms, an effect not detected in the placebo group. Conversely, reductions in TNFR1 levels were associated with increased global cortical thickness in infliximab- (r = -0.581, p = 0.029), but not placebo-treated, patients (r = 0.196, p = 0.501). In conclusion, we report that NEVs revealed that infliximab engaged the TNFR/NF-κB neuro-inflammatory pathway in individuals with BD, in a childhood trauma-dependent manner, which was associated with clinical response and brain structural changes.

Preclinical translation of exosomes derived from mesenchymal stem/stromal cells

Exosomes are nanovesicles secreted by virtually all cells. Exosomes mediate the horizontal transfer of various macromolecules previously believed to be cell-autonomous in nature, including nonsecretory proteins, various classes of RNA, metabolites, and lipid membrane-associated factors. Exosomes derived from mesenchymal stem/stromal cells (MSCs) appear to be particularly beneficial for enhancing recovery in various models of disease. To date, there have been more than 200 preclinical studies of exosome-based therapies in a number of different animal models. Despite a growing number of studies reporting the therapeutic properties of MSC-derived exosomes, their underlying mechanism of action, pharmacokinetics, and scalable manufacturing remain largely outstanding questions. Here, we review the global trends associated with preclinical development of MSC-derived exosome-based therapies, including immunogenicity, source of exosomes, isolation methods, biodistribution, and disease categories tested to date. Although the in vivo data assessing the therapeutic properties of MSC-exosomes published to date are promising, several outstanding questions remain to be answered that warrant further preclinical investigation.

(-)-Phenserine tartrate (PhenT) as a treatment for traumatic brain injury

Aim

Traumatic brain injury (TBI) is one of the most common causes of morbidity and mortality of both young adults and the elderly, and is a key contributing factor in about 30% of all injury‐associated deaths occurring within the United States of America. Albeit substantial impact has been made to improve our comprehension of the mechanisms that underpin the primary and secondary injury stages initiated by a TBI incident, this knowledge has yet to successfully translate into the development of an effective TBI pharmacological treatment. Developing consent suggests that a TBI can concomitantly trigger multiple TBI‐linked cascades that then progress in parallel and, if correct, the multifactorial nature of TBI would make the discovery of a single effective mechanism‐targeted drug unlikely.

Discussion

We review recent data indicating that the small molecular weight drug (−)‐phenserine tartrate (PhenT), originally developed for Alzheimer's disease (AD), effectively inhibits a broad range of mechanisms pertinent to mild (m) and moderate (mod)TBI, which in combination underpin the ensuing cognitive and motor impairments. In cellular and animal models at clinically translatable doses, PhenT mitigated mTBI‐ and modTBI‐induced programmed neuronal cell death (PNCD), oxidative stress, glutamate excitotoxicity, neuroinflammation, and effectively reversed injury‐induced gene pathways leading to chronic neurodegeneration. In addition to proving efficacious in well‐characterized animal TBI models, significantly mitigating cognitive and motor impairments, the drug also has demonstrated neuroprotective actions against ischemic stroke and the organophosphorus nerve agent and chemical weapon, soman.

Conclusion

In the light of its tolerability in AD clinical trials, PhenT is an agent that can be fast‐tracked for evaluation in not only civilian TBI, but also as a potentially protective agent in battlefield conditions where TBI and chemical weapon exposure are increasingly jointly occurring.

miR-212 and miR-132 Are Downregulated in Neurally Derived Plasma Exosomes of Alzheimer's Patients

It was recently discovered that brain cells release extracellular vesicles (EV) which can pass from brain into blood. These findings raise the possibility that brain-derived EV’s present in blood can be used to monitor disease processes occurring in the cerebrum. Since the levels of certain micro-RNAs (miRNAs) have been reported to be altered in Alzheimer’s disease (AD) brain, we sought to assess miRNA dysregulation in AD brain tissue and to determine if these changes were reflected in neural EVs isolated from blood of subjects with AD. To this end, we employed high-content miRNA arrays to search for differences in miRNAs in RNA pools from brain tissue of AD (n = 5), high pathological control (HPC) (n = 5), or cognitively intact pathology-free controls (n = 5). Twelve miRNAs were altered by >1.5-fold in AD compared to controls, and six of these were also changed compared to HPCs. Analysis of hits in brain extracts from 11 AD, 7 HPCs and 9 controls revealed a similar fold difference in these six miRNAs, with three showing statistically significant group differences and one with a strong trend toward group differences. Thereafter, we focused on the four miRNAs that showed group differences and measured their content in neurally derived blood EVs isolated from 63 subjects: 16 patients with early stage dementia and a CSF Aβ42+ tau profile consistent with AD, 16 individuals with mild cognitive impairment (MCI) and an AD CSF profile, and 31 cognitively intact controls with normal CSF Aβ42+ tau levels. ROC analysis indicated that measurement of miR-132-3p in neurally-derived plasma EVs showed good sensitivity and specificity to diagnose AD, but did not effectively separate individuals with AD-MCI from controls. Moreover, when we measured the levels of a related miRNA, miR-212, we found that this miRNA was also decreased in neural EVs from AD patients compared to controls. Our results suggest that measurement of miR-132 and miR-212 in neural EVs should be further investigated as a diagnostic aid for AD and as a potential theragnostic.

Neuron-Derived Plasma Exosome Proteins after Remote Traumatic Brain Injury

To identify long-term effects of traumatic brain injury (TBI) on levels of plasma neuron-derived exosome (NDE) protein biomarkers of cognitive impairment (CI), plasmas were obtained from four groups of older veterans, who were matched for age and sex: no TBI or CI (n = 42), no TBI with CI (n = 19), TBI without CI (n = 21), and TBI with CI (n = 26). The TBI was sustained 12 to 74 years before the study in 75%. The NDEs were enriched by sequential precipitation and anti-L1CAM antibody immunoabsorption, and extracted protein biomarkers were quantified by enzyme-linked immunosorbent assays. Chronic NDE biomarkers known to increase for three to 12 months after TBI, including cellular prion protein (PrPc), synaptogyrin-3, P-T181-tau, P-S396-tau, Aβ42, and interleukin (IL)-6, were elevated significantly in subjects who had TBI and CI compared with controls with TBI but no CI. Chronic NDE biomarker levels in subjects without TBI showed significantly higher levels of PrPc, synaptogyrin-3, P-T181-tau, and Aβ42, but not P-S396-tau and IL-6, in those with CI compared with controls without CI. The acute NDE biomarkers claudin-5, annexin VII, and aquaporin-4 were not increased in either group with CI. The NDE biomarkers P-S396-tau and IL-6, which are increased distinctively with CI after TBI, may prove useful in evaluating CI in older patients. Aβ42 and P-tau species, as well as their respective putative receptors, PrPc and synaptogyrin-3, remain elevated for decades after TBI and may mediate TBI-associated CI and be useful targets for development of drugs.