Proteomic changes in the human cerebrovasculature in Alzheimer's disease and related tauopathies linked to peripheral biomarkers in plasma and cerebrospinal fluid

INTRODUCTION

Cerebrovascular dysfunction is a pathological hallmark of Alzheimer's disease (AD). Nevertheless, detecting cerebrovascular changes within bulk tissues has limited our ability to characterize proteomic alterations from less abundant cell types.

METHODS

We conducted quantitative proteomics on bulk brain tissues and isolated cerebrovasculature from the same individuals, encompassing control (N = 28), progressive supranuclear palsy (PSP) (N = 18), and AD (N = 21) cases.

RESULTS

Protein co-expression network analysis identified unique cerebrovascular modules significantly correlated with amyloid plaques, cerebrovascular amyloid angiopathy (CAA), and/or tau pathology. The protein products within AD genetic risk loci were concentrated within cerebrovascular modules. The overlap between differentially abundant proteins in AD cerebrospinal fluid (CSF) and plasma with cerebrovascular network highlighted a significant increase of matrisome proteins, SMOC1 and SMOC2, in CSF, plasma, and brain.

DISCUSSION

These findings enhance our understanding of cerebrovascular deficits in AD, shedding light on potential biomarkers associated with CAA and vascular dysfunction in neurodegenerative diseases.

Native-state proteomics of Parvalbumin interneurons identifies unique molecular signatures and vulnerabilities to early Alzheimer's pathology

Dysfunction in fast-spiking parvalbumin interneurons (PV-INs) may represent an early pathophysiological perturbation in Alzheimer's Disease (AD). Defining early proteomic alterations in PV-INs can provide key biological and translationally-relevant insights. We used cell-type-specific in-vivo biotinylation of proteins (CIBOP) coupled with mass spectrometry to obtain native-state PV-IN proteomes. PV-IN proteomic signatures include high metabolic and translational activity, with over-representation of AD-risk and cognitive resilience-related proteins. In bulk proteomes, PV-IN proteins were associated with cognitive decline in humans, and with progressive neuropathology in humans and the 5xFAD mouse model of Aβ pathology. PV-IN CIBOP in early stages of Aβ pathology revealed signatures of increased mitochondria and metabolism, synaptic and cytoskeletal disruption and decreased mTOR signaling, not apparent in whole-brain proteomes. Furthermore, we demonstrated pre-synaptic defects in PV-to-excitatory neurotransmission, validating our proteomic findings. Overall, in this study we present native-state proteomes of PV-INs, revealing molecular insights into their unique roles in cognitive resiliency and AD pathogenesis.

Proteomic Changes in the Human Cerebrovasculature in Alzheimer's Disease and Related Tauopathies Linked to Peripheral Biomarkers in Plasma and Cerebrospinal Fluid

Dysfunction of the neurovascular unit stands as a significant pathological hallmark of Alzheimer's disease (AD) and age-related neurodegenerative diseases. Nevertheless, detecting vascular changes in the brain within bulk tissues has proven challenging, limiting our ability to characterize proteomic alterations from less abundant cell types. To address this challenge, we conducted quantitative proteomic analyses on both bulk brain tissues and cerebrovascular-enriched fractions from the same individuals, encompassing cognitively unimpaired control, progressive supranuclear palsy (PSP), and AD cases. Protein co-expression network analysis identified modules unique to the cerebrovascular fractions, specifically enriched with pericytes, endothelial cells, and smooth muscle cells. Many of these modules also exhibited significant correlations with amyloid plaques, cerebral amyloid angiopathy (CAA), and/or tau pathology in the brain. Notably, the protein products within AD genetic risk loci were found concentrated within modules unique to the vascular fractions, consistent with a role of cerebrovascular deficits in the etiology of AD. To prioritize peripheral AD biomarkers associated with vascular dysfunction, we assessed the overlap between differentially abundant proteins in AD cerebrospinal fluid (CSF) and plasma with a vascular-enriched network modules in the brain. This analysis highlighted matrisome proteins, SMOC1 and SMOC2, as being increased in CSF, plasma, and brain. Immunohistochemical analysis revealed SMOC1 deposition in both parenchymal plaques and CAA in the AD brain, whereas SMOC2 was predominantly localized to CAA. Collectively, these findings significantly enhance our understanding of the involvement of cerebrovascular abnormalities in AD, shedding light on potential biomarkers and molecular pathways associated with CAA and vascular dysfunction in neurodegenerative diseases.

Proteomic Signaling of Dual-Specificity Phosphatase 4 (DUSP4) in Alzheimer's Disease

DUSP4 is a member of the DUSP (dual-specificity phosphatase) subfamily that is selective to the mitogen-activated protein kinases (MAPK) and has been implicated in a range of biological processes and functions in Alzheimer's disease (AD). In this study, we utilized the stereotactic delivery of adeno-associated virus (AAV)-DUSP4 to overexpress DUSP4 in the dorsal hippocampus of 5xFAD and wildtype (WT) mice, then used mass spectrometry (MS)-based proteomics along with the label-free quantification to profile the proteome and phosphoproteome in the hippocampus. We identified protein expression and phosphorylation patterns modulated in 5xFAD mice and examined the sex-specific impact of DUSP4 overexpression on the 5xFAD proteome/phosphoproteome. In 5xFAD mice, a substantial number of proteins were up- or down-regulated in both male and female mice in comparison to age and sex-matched WT mice, many of which are involved in AD-related biological processes, such as activated immune response or suppressed synaptic activities. Many proteins in pathways, such as immune response were found to be suppressed in response to DUSP4 overexpression in male 5xFAD mice. In contrast, such a shift was absent in female mice. For the phosphoproteome, we detected an array of phosphorylation sites regulated in 5xFAD compared to WT and modulated via DUSP4 overexpression in each sex. Interestingly, 5xFAD- and DUSP4-associated phosphorylation changes occurred in opposite directions. Strikingly, both the 5xFAD- and DUSP4-associated phosphorylation changes were found to be mostly in neurons and play key roles in neuronal processes and synaptic functions. Site-centric pathway analysis revealed that both the 5xFAD- and DUSP4-associated phosphorylation sites were enriched for a number of kinase sets in females but only a limited number of sets of kinases in male mice. Taken together, our results suggest that male and female 5xFAD mice responded to DUSP4 overexpression via shared and sex-specific molecular mechanisms, which might underly similar reductions in amyloid pathology in both sexes while learning deficits were reduced in only females with DUSP4 overexpression. Finally, we validated our findings with the sex-specific AD-associated proteomes in human cohorts and further developed DUSP4-centric proteomic network models and signaling maps for each sex.

Identification of State-Specific Proteomic and Transcriptomic Signatures of Microglia-Derived Extracellular Vesicles

Microglia are resident immune cells of the brain that play important roles in mediating inflammatory responses in several neurological diseases via direct and indirect mechanisms. One indirect mechanism may involve extracellular vesicle (EV) release, so that the molecular cargo transported by microglia-derived EVs can have functional effects by facilitating intercellular communication. The molecular composition of microglia-derived EVs, and how microglial activation states impact EV composition and EV-mediated effects in neuroinflammation, remain poorly understood. We hypothesize that microglia-derived EVs have unique molecular profiles that are determined by microglial activation state. Using size-exclusion chromatography to purify EVs from BV2 microglia, combined with proteomic (label-free quantitative mass spectrometry or LFQ-MS) and transcriptomic (mRNA and noncoding RNA seq) methods, we obtained comprehensive molecular profiles of microglia-derived EVs. LFQ-MS identified several classic EV proteins (tetraspanins, ESCRT machinery, and heat shock proteins), in addition to over 200 proteins not previously reported in the literature. Unique mRNA and microRNA signatures of microglia-derived EVs were also identified. After treating BV2 microglia with lipopolysaccharide (LPS), interleukin-10, or transforming growth factor beta, to mimic pro-inflammatory, anti-inflammatory, or homeostatic states, respectively, LFQ-MS and RNA seq revealed novel state-specific proteomic and transcriptomic signatures of microglia-derived EVs. Particularly, LPS treatment had the most profound impact on proteomic and transcriptomic compositions of microglia-derived EVs. Furthermore, we found that EVs derived from LPS-activated microglia were able to induce pro-inflammatory transcriptomic changes in resting responder microglia, confirming the ability of microglia-derived EVs to relay functionally relevant inflammatory signals. These comprehensive microglia-EV molecular datasets represent important resources for the neuroscience and omics communities and provide novel insights into the role of microglia-derived EVs in neuroinflammation.

Entorhinal cortex vulnerability to human APP expression promotes hyperexcitability and tau pathology

Preventative treatment for Alzheimer's Disease is of dire importance, and yet, cellular mechanisms underlying early regional vulnerability in Alzheimer's Disease remain unknown. In human patients with Alzheimer's Disease, one of the earliest observed pathophysiological correlates to cognitive decline is hyperexcitability1. In mouse models, early hyperexcitability has been shown in the entorhinal cortex, the first cortical region impacted by Alzheimer's Disease2-4. The origin of hyperexcitability in early-stage disease and why it preferentially emerges in specific regions is unclear. Using cortical-region and cell-type- specific proteomics and patch-clamp electrophysiology, we uncovered differential susceptibility to human-specific amyloid precursor protein (hAPP) in a model of sporadic Alzheimer's. Unexpectedly, our findings reveal that early entorhinal hyperexcitability may result from intrinsic vulnerability of parvalbumin interneurons, rather than the suspected layer II excitatory neurons. This vulnerability of entorhinal PV interneurons is specific to hAPP, as it could not be recapitulated with increased murine APP expression. Furthermore, the Somatosensory Cortex showed no such vulnerability to adult-onset hAPP expression, likely resulting from PV-interneuron variability between the two regions based on physiological and proteomic evaluations. Interestingly, entorhinal hAPP-induced hyperexcitability was quelled by co-expression of human Tau at the expense of increased pathological tau species. This study suggests early disease interventions targeting non-excitatory cell types may protect regions with early vulnerability to pathological symptoms of Alzheimer's Disease and downstream cognitive decline.

Telemedicine impact on post-stroke outpatient follow-up in an academic healthcare network during the COVID-19 pandemic

BACKGROUND

The expansion of telemedicine associated with the COVID-19 pandemic has influenced outpatient medical care. The objective of our study was to determine the impact of telemedicine on post-acute stroke clinic follow-up.

METHODS

We retrospectively evaluated the impact of telemedicine in Emory Healthcare, an academic healthcare system of comprehensive and primary stroke centers in Atlanta, Georgia, on post-hospital stroke clinic follow-up. We compared the frequency of 90-day follow-up in a centralized subspecialty stroke clinic among patients hospitalized before the local COVID-19 pandemic (January 1, 2019- February 28, 2020), during (March 1- April 30, 2020) and after telemedicine implementation (May 1- December 31, 2020). A comparison was made across hospitals less than 1 mile, 10 miles, and 25 miles from the stroke clinic.

RESULTS

Of 1096 ischemic stroke patients discharged home or to a rehab facility during the study period, 342 (31%) had follow-up in the Emory Stroke Clinic (comprehensive stroke center 46%, primary stroke center 10 miles away 18%, primary stroke center 25 miles away 14%). Overall, 90-day follow-up increased from 19% to 41% after telemedicine implementation (p<0.001) with telemedicine appointments amounting for up to 28% of all follow-up visits. In multivariable analysis, factors associated with teleneurology follow-up (vs no follow-up) included discharge from the comprehensive stroke center, thrombectomy treatment, private insurance, private transport to the hospital, NIHSS 0-5 and history of dyslipidemia.

CONCLUSIONS

Despite telemedicine implementation at an academic healthcare network successfully increasing post-stroke discharge follow-up in a centralized subspecialty stroke clinic, the majority of patients did not complete 90-day follow-up during the COVID-19 pandemic.

Identification of state-specific proteomic and transcriptomic signatures of microglia-derived extracellular vesicles

Microglia are resident immune cells of the brain that play important roles in mediating inflammatory responses in several neurological diseases via direct and indirect mechanisms. One indirect mechanism may involve extracellular vesicle (EV) release, so that the molecular cargo transported by microglia-derived EVs can have functional effects by facilitating intercellular communication. The molecular composition of microglia-derived EVs, and how microglial activation states impacts EV composition and EV-mediated effects in neuroinflammation, remain poorly understood. We hypothesize that microglia-derived EVs have unique molecular profiles that are determined by microglial activation state. Using size-exclusion chromatography to purify EVs from BV2 microglia, combined with proteomic (label-free quantitative mass spectrometry or LFQ-MS) and transcriptomic (mRNA and non-coding RNA seq) methods, we obtained comprehensive molecular profiles of microglia-derived EVs. LFQ-MS identified several classic EV proteins (tetraspanins, ESCRT machinery, and heat shock proteins), in addition to over 200 proteins not previously reported in the literature. Unique mRNA and microRNA signatures of microglia-derived EVs were also identified. After treating BV2 microglia with lipopolysaccharide (LPS), interleukin-10, or transforming growth factor beta, to mimic pro-inflammatory, anti-inflammatory, or homeostatic states, respectively, LFQ-MS and RNA seq revealed novel state-specific proteomic and transcriptomic signatures of microglia-derived EVs. Particularly, LPS treatment had the most profound impact on proteomic and transcriptomic compositions of microglia-derived EVs. Furthermore, we found that EVs derived from LPS-activated microglia were able to induce pro-inflammatory transcriptomic changes in resting responder microglia, confirming the ability of microglia-derived EVs to relay functionally-relevant inflammatory signals. These comprehensive microglia-EV molecular datasets represent important resources for the neuroscience and glial communities, and provide novel insights into the role of microglia-derived EVs in neuroinflammation.

Advances in proteomic phenotyping of microglia in neurodegeneration

Microglia are dynamic resident immune cells of the central nervous system (CNS) that sense, survey, and respond to changes in their environment. In disease states, microglia transform from homeostatic to diverse molecular phenotypic states that play complex and causal roles in neurologic disease pathogenesis, as evidenced by the identification of microglial genes as genetic risk factors for neurodegenerative disease. While advances in transcriptomic profiling of microglia from the CNS of humans and animal models have provided transformative insights, the transcriptome is only modestly reflective of the proteome. Proteomic profiling of microglia is therefore more likely to provide functionally and therapeutically relevant targets. In this review, we discuss molecular insights gained from transcriptomic studies of microglia in the context of Alzheimer's disease as a prototypic neurodegenerative disease, and highlight existing and emerging approaches for proteomic profiling of microglia derived from in vivo model systems and human brain.

Factors associated with stroke after COVID-19 vaccination: a statewide analysis

Background

The objective of our study was to evaluate vaccine type, COVID-19 infection, and their association with stroke soon after COVID-19 vaccination.

Methods

In a retrospective cohort study, we estimated the 21-day post-vaccination incidence of stroke among the recipients of the first dose of a COVID-19 vaccine. We linked the Georgia Immunization Registry with the Georgia Coverdell Acute Stroke Registry and the Georgia State Electronic Notifiable Disease Surveillance System data to assess the relative risk of stroke by the vaccine type.

Results

Approximately 5 million adult Georgians received at least one COVID-19 vaccine between 1 December 2020 and 28 February 2022: 54% received BNT162b2, 41% received mRNA-1273, and 5% received Ad26.COV2.S. Those with concurrent COVID-19 infection within 21 days post-vaccination had an increased risk of ischemic (OR = 8.00, 95% CI: 4.18, 15.31) and hemorrhagic stroke (OR = 5.23, 95% CI: 1.11, 24.64) with no evidence for interaction between the vaccine type and concurrent COVID-19 infection. The 21-day post-vaccination incidence of ischemic stroke was 8.14, 11.14, and 10.48 per 100,000 for BNT162b2, mRNA-1273, and Ad26.COV2.S recipients, respectively. After adjusting for age, race, gender, and COVID-19 infection status, there was a 57% higher risk (OR = 1.57, 95% CI: 1.02, 2.42) for ischemic stroke within 21 days of vaccination associated with the Ad26.COV2.S vaccine compared to BNT162b2; there was no difference in stroke risk between mRNA-1273 and BNT162b2.

Conclusion

Concurrent COVID-19 infection had the strongest association with early ischemic and hemorrhagic stroke after the first dose of COVID-19 vaccination. Although not all determinants of stroke, particularly comorbidities, were considered in this analysis, the Ad26.COV2.S vaccine was associated with a higher risk of early post-vaccination ischemic stroke than BNT162b2.

Profiling the neuroimmune cascade in 3xTg mice exposed to successive mild traumatic brain injuries

Repetitive mild traumatic brain injuries (rmTBI) sustained within a window of vulnerability can result in long term cognitive deficits, depression, and eventual neurodegeneration associated with tau pathology, amyloid beta (Aβ) plaques, gliosis, and neuronal and functional loss. However, we have limited understanding of how successive injuries acutely affect the brain to result in these devastating long-term consequences. In the current study, we addressed the question of how repeated injuries affect the brain in the acute phase of injury (<24hr) by exposing the 3xTg-AD mouse model of tau and Aβ pathology to successive (1x, 3x, 5x) once-daily weight drop closed-head injuries and quantifying immune markers, pathological markers, and transcriptional profiles at 30min, 4hr, and 24hr after each injury. We used young adult mice (2-4 months old) to model the effects of rmTBI relevant to young adult athletes, and in the absence of significant tau and Aβ pathology. Importantly, we identified pronounced sexual dimorphism, with females eliciting more differentially expressed proteins after injury compared to males. Specifically, females showed: 1) a single injury caused a decrease in neuron-enriched genes inversely correlated with inflammatory protein expression as well as an increase in AD-related genes within 24hr, 2) each injury significantly increased expression of a group of cortical cytokines (IL-1α, IL-1β, IL-2, IL-9, IL-13, IL-17, KC) and MAPK phospho-proteins (phospho-Atf2, phospho-Mek1), several of which were co-labeled with neurons and correlated with phospho-tau, and 3) repetitive injury caused increased expression of genes associated with astrocyte reactivity and immune function. Collectively our data suggest that neurons respond to a single injury within 24h, while other cell types including astrocytes transition to inflammatory phenotypes within days of repetitive injury.

Cellular Proteomic Profiling Using Proximity Labeling by TurboID-NES in Microglial and Neuronal Cell Lines

Different brain cell types play distinct roles in brain development and disease. Molecular characterization of cell-specific mechanisms using cell type-specific approaches at the protein (proteomic) level can provide biological and therapeutic insights. To overcome the barriers of conventional isolation-based methods for cell type-specific proteomics, in vivo proteomic labeling with proximity-dependent biotinylation of cytosolic proteins using biotin ligase TurboID, coupled with mass spectrometry (MS) of labeled proteins, emerged as a powerful strategy for cell type-specific proteomics in the native state of cells without the need for cellular isolation. To complement in vivo proximity labeling approaches, in vitro studies are needed to ensure that cellular proteomes using the TurboID approach are representative of the whole-cell proteome and capture cellular responses to stimuli without disruption of cellular processes. To address this, we generated murine neuroblastoma (N2A) and microglial (BV2) lines stably expressing cytosolic TurboID to biotinylate the cellular proteome for downstream purification and analysis using MS. TurboID-mediated biotinylation captured 59% of BV2 and 65% of N2A proteomes under homeostatic conditions. TurboID labeled endolysosome, translation, vesicle, and signaling proteins in BV2 microglia and synaptic, neuron projection, and microtubule proteins in N2A neurons. TurboID expression and biotinylation minimally impacted homeostatic cellular proteomes of BV2 and N2A cells and did not affect lipopolysaccharide-mediated cytokine production or resting cellular respiration in BV2 cells. MS analysis of the microglial biotin-labeled proteins captured the impact of lipopolysaccharide treatment (>500 differentially abundant proteins) including increased canonical proinflammatory proteins (Il1a, Irg1, and Oasl1) and decreased anti-inflammatory proteins (Arg1 and Mgl2).

Native-state proteomics of Parvalbumin interneurons identifies novel molecular signatures and metabolic vulnerabilities to early Alzheimer's disease pathology

One of the earliest pathophysiological perturbations in Alzheimer's Disease (AD) may arise from dysfunction of fast-spiking parvalbumin (PV) interneurons (PV-INs). Defining early protein-level (proteomic) alterations in PV-INs can provide key biological and translationally relevant insights. Here, we use cell-type-specific in vivo biotinylation of proteins (CIBOP) coupled with mass spectrometry to obtain native-state proteomes of PV interneurons. PV-INs exhibited proteomic signatures of high metabolic, mitochondrial, and translational activity, with over-representation of causally linked AD genetic risk factors. Analyses of bulk brain proteomes indicated strong correlations between PV-IN proteins with cognitive decline in humans, and with progressive neuropathology in humans and mouse models of Aβ pathology. Furthermore, PV-IN-specific proteomes revealed unique signatures of increased mitochondrial and metabolic proteins, but decreased synaptic and mTOR signaling proteins in response to early Aβ pathology. PV-specific changes were not apparent in whole-brain proteomes. These findings showcase the first native state PV-IN proteomes in mammalian brain, revealing a molecular basis for their unique vulnerabilities in AD.

APOE expression and secretion are modulated by mitochondrial dysfunction

Mitochondria influence cellular function through both cell-autonomous and non-cell autonomous mechanisms, such as production of paracrine and endocrine factors. Here, we demonstrate that mitochondrial regulation of the secretome is more extensive than previously appreciated, as both genetic and pharmacological disruption of the electron transport chain caused upregulation of the Alzheimer's disease risk factor apolipoprotein E (APOE) and other secretome components. Indirect disruption of the electron transport chain by gene editing of SLC25A mitochondrial membrane transporters as well as direct genetic and pharmacological disruption of either complexes I, III, or the copper-containing complex IV of the electron transport chain elicited upregulation of APOE transcript, protein, and secretion, up to 49-fold. These APOE phenotypes were robustly expressed in diverse cell types and iPSC-derived human astrocytes as part of an inflammatory gene expression program. Moreover, age- and genotype-dependent decline in brain levels of respiratory complex I preceded an increase in APOE in the 5xFAD mouse model. We propose that mitochondria act as novel upstream regulators of APOE-dependent cellular processes in health and disease.

Cincinnati Prehospital Stroke Scale Implementation of an Urban County Severity-Based Stroke Triage Protocol: Impact and Outcomes on a Comprehensive Stroke Center

BACKGROUND AND PURPOSE

Screening scales are recommended to assist field-based triage of acute stroke patients to designated stroke centers. Cincinnati prehospital stroke scale (CPSS) is a commonly used prehospital stroke screening tool and has been validated to identify large vessel occlusion (LVO). This study addresses the impact of county-based CPSS implementation to triage suspected LVO patients to a comprehensive stroke center (CSC).

MATERIALS AND METHODS

Dekalb County in Atlanta, Georgia, implemented CPSS-based protocol with score of 3 and last seen normal time < 24 h mandating transfer to the nearest CSC if the added bypass time was <15 min. Frequency of stroke codes, LVO, IV-tPA use, and thrombectomy treatment were compared six months before and after protocol change (November 1, 2020).

RESULTS

During the study period, 907 stroke patients presented to the CSC by EMS, including 289 (32%) with CPSS score 3. There was an increase in monthly ischemic stroke volume (pre-16 ± 2 vs.19 ± 3 p = 0.03), LVO (pre-4.3 ± 1.7 vs. post-7.0 ± 2.4; p = 0.03), EVT (pre-15% vs. post-30%; p = 0.001), without significant increase in stroke mimic volume or delay in mean time from last seen normal to IV-tPA (pre-165 ± 66, post-158 ± 49 min; p = 0.35). CPSS score 3 was associated with increased likelihood of LVO diagnosis (OR 8.5, 95% CI 5.0-14.4; p = 0.001) and decreased the likelihood of stroke mimics (OR 0.66, 95% CI 0.50-0.88; p = 0.004).

CONCLUSION

CPSS is a quick, easy to implement, and reliable prehospital severity scale for EMS to triage LVO to CSC without delaying IV-tPA treatment or significantly increasing stroke mimics.

Biophysical Kv3 channel alterations dampen excitability of cortical PV interneurons and contribute to network hyperexcitability in early Alzheimer's

In Alzheimer’s disease (AD), a multitude of genetic risk factors and early biomarkers are known. Nevertheless, the causal factors responsible for initiating cognitive decline in AD remain controversial. Toxic plaques and tangles correlate with progressive neuropathology, yet disruptions in circuit activity emerge before their deposition in AD models and patients. Parvalbumin (PV) interneurons are potential candidates for dysregulating cortical excitability as they display altered action potential (AP) firing before neighboring excitatory neurons in prodromal AD. Here, we report a novel mechanism responsible for PV hypoexcitability in young adult familial AD mice. We found that biophysical modulation of K_v3 channels, but not changes in their mRNA or protein expression, were responsible for dampened excitability in young 5xFAD mice. These K⁺ conductances could efficiently regulate near-threshold AP firing, resulting in gamma-frequency-specific network hyperexcitability. Thus, biophysical ion channel alterations alone may reshape cortical network activity prior to changes in their expression levels. Our findings demonstrate an opportunity to design a novel class of targeted therapies to ameliorate cortical circuit hyperexcitability in early AD.

Brain Cell Type-Specific Nuclear Proteomics Is Imperative to Resolve Neurodegenerative Disease Mechanisms

Neurodegenerative diseases (NDs) involve complex cellular mechanisms that are incompletely understood. Emerging findings have revealed that disruption of nuclear processes play key roles in ND pathogenesis. The nucleus is a nexus for gene regulation and cellular processes that together, may underlie pathomechanisms of NDs. Furthermore, many genetic risk factors for NDs encode proteins that are either present in the nucleus or are involved in nuclear processes (for example, RNA binding proteins, epigenetic regulators, or nuclear-cytoplasmic transport proteins). While recent advances in nuclear transcriptomics have been significant, studies of the nuclear proteome in brain have been relatively limited. We propose that a comprehensive analysis of nuclear proteomic alterations of various brain cell types in NDs may provide novel biological and therapeutic insights. This may be feasible because emerging technical advances allow isolation and investigation of intact nuclei from post-mortem frozen human brain tissue with cell type-specific and single-cell resolution. Accordingly, nuclei of various brain cell types harbor unique protein markers which can be used to isolate cell-type specific nuclei followed by down-stream proteomics by mass spectrometry. Here we review the literature providing a rationale for investigating proteomic changes occurring in nuclei in NDs and then highlight the potential for brain cell type-specific nuclear proteomics to enhance our understanding of distinct cellular mechanisms that drive ND pathogenesis.

Cell type-specific biotin labeling in vivo resolves regional neuronal and astrocyte proteomic differences in mouse brain

Proteomic profiling of brain cell types using isolation-based strategies pose limitations in resolving cellular phenotypes representative of their native state. We describe a mouse line for cell type-specific expression of biotin ligase TurboID, for in vivo biotinylation of proteins. Using adenoviral and transgenic approaches to label neurons, we show robust protein biotinylation in neuronal soma and axons throughout the brain, allowing quantitation of over 2000 neuron-derived proteins spanning synaptic proteins, transporters, ion channels and disease-relevant druggable targets. Next, we contrast Camk2a-neuron and Aldh1l1-astrocyte proteomes and identify brain region-specific proteomic differences within both cell types, some of which might potentially underlie the selective vulnerability to neurological diseases. Leveraging the cellular specificity of proteomic labeling, we apply an antibody-based approach to uncover differences in neuron and astrocyte-derived signaling phospho-proteins and cytokines. This approach will facilitate the characterization of cell-type specific proteomes in a diverse number of tissues under both physiological and pathological states.

BIN1 is a key regulator of proinflammatory and neurodegeneration-related activation in microglia

BACKGROUND

The BIN1 locus contains the second-most significant genetic risk factor for late-onset Alzheimer's disease. BIN1 undergoes alternate splicing to generate tissue- and cell-type-specific BIN1 isoforms, which regulate membrane dynamics in a range of crucial cellular processes. Whilst the expression of BIN1 in the brain has been characterized in neurons and oligodendrocytes in detail, information regarding microglial BIN1 expression is mainly limited to large-scale transcriptomic and proteomic data. Notably, BIN1 protein expression and its functional roles in microglia, a cell type most relevant to Alzheimer's disease, have not been examined in depth.

METHODS

Microglial BIN1 expression was analyzed by immunostaining mouse and human brain, as well as by immunoblot and RT-PCR assays of isolated microglia or human iPSC-derived microglial cells. Bin1 expression was ablated by siRNA knockdown in primary microglial cultures in vitro and Cre-lox mediated conditional deletion in adult mouse brain microglia in vivo. Regulation of neuroinflammatory microglial signatures by BIN1 in vitro and in vivo was characterized using NanoString gene panels and flow cytometry methods. The transcriptome data was explored by in silico pathway analysis and validated by complementary molecular approaches.

RESULTS

Here, we characterized microglial BIN1 expression in vitro and in vivo and ascertained microglia expressed BIN1 isoforms. By silencing Bin1 expression in primary microglial cultures, we demonstrate that BIN1 regulates the activation of proinflammatory and disease-associated responses in microglia as measured by gene expression and cytokine production. Our transcriptomic profiling revealed key homeostatic and lipopolysaccharide (LPS)-induced inflammatory response pathways, as well as transcription factors PU.1 and IRF1 that are regulated by BIN1. Microglia-specific Bin1 conditional knockout in vivo revealed novel roles of BIN1 in regulating the expression of disease-associated genes while counteracting CX3CR1 signaling. The consensus from in vitro and in vivo findings showed that loss of Bin1 impaired the ability of microglia to mount type 1 interferon responses to proinflammatory challenge, particularly the upregulation of a critical type 1 immune response gene, Ifitm3.

CONCLUSIONS

Our convergent findings provide novel insights into microglial BIN1 function and demonstrate an essential role of microglial BIN1 in regulating brain inflammatory response and microglial phenotypic changes. Moreover, for the first time, our study shows a regulatory relationship between Bin1 and Ifitm3, two Alzheimer's disease-related genes in microglia. The requirement for BIN1 to regulate Ifitm3 upregulation during inflammation has important implications for inflammatory responses during the pathogenesis and progression of many neurodegenerative diseases.

Simultaneous RNA and protein profiling using a TurboID proximity-labeling strategy

BACKGROUND

Biologically relevant insights into cellular disease mechanisms of neurons and glia can be obtained by complimentary molecular profiling of the transcriptome and proteome of these cells. While mutually exclusive pipelines are available, the information surveyed is often from different samples leading to poor correlation between the transcriptome and proteome. Our goal was to develop a method for concomitant cell type-specific analyses of RNA and protein.

METHOD

We utilized a proximity-labeling strategy that uses the biotin ligase, TurboID, to efficiently label the proteome, in a mouse microglial BV2 cell line. We created a stable BV2-TurboID cell line that expresses TurboID fused to a nuclear export sequence. Biotin treatment of BV2-TurboID cells resulted in robust biotinylation of the cellular proteome as confirmed by Western blot and by label-free quantitation mass spectrometry (LFQ-MS) of biotinylated proteins enriched with streptavidin beads. LFQ-MS revealed that TurboID biotinylates several RNA-binding proteins (RBPs) including ribosomal units, suggesting that transcripts associated with RBPs may also be pulled down simultaneously with proteins. To test this, we homogenized BV2-Turbo and control BV2 cells, enriched biotinylated proteins with streptavidin beads while maintaining RNA-protein interactions, and then eluted RNA.

RESULT

Quality control studies showed negligible mRNA from streptavidin pulldowns from control BV2 cells, while BV2-TurboID pulldowns had larger mRNA yields with high quality. NanoString neuroinflammatory profiling (800 genes) of whole cell RNA from control BV2 and BV2-TurboID cells and streptavidin pulldowns from both cell types were performed. We observed a 23-fold higher mRNA yield in the BV2-TurboID pulldowns compared to control BV2 cells for 550 genes included in the analyses. Transcript abundances from total RNA and BV2-TurboID pulldowns were highly comparable (R² =0.97; no differentially expressed genes) with equivalent abundance of microglial genes (e.g., Spp1 and Apoe) suggesting a faithful transcriptome capture.

CONCLUSION

Our novel TurboID proximity labeling approach can simultaneously capture cell type-specific transcriptomes and proteomes. We are now validating this method in other cell types using RNA-sequencing and MS approaches. Once validated, this concurrent RNA and protein profiling approach can be applied to in vivo and ex vivo model systems to investigate the distinct roles brain cell types play in development, aging, and disease.

Identification of Kv1.3 potassium channel interacting proteins in mammalian cells

BACKGROUND

Alzheimer's disease (AD) is a devastating neurodegenerative disease characterized by progressive neuronal loss, accumulation of amyloid-beta(Aβ) plaques, and neuroinflammation. Microglia, the immune cell of the brain, transition to disease associated microglia (DAM) in AD. A subset of DAM, known as proinflammatory DAM, promote neuronal injury and release proinflammatory cytokines. Our lab established that proinflammatory DAM highly express Kv1.3 potassium channel, which consist of a homotetramer of Kv1.3 that interacts with a homotetramer of Kvβ2. Blockade of the Kv1.3 channel reduces microglial immune responses in mouse models. Both Kv1.3 and Kvβ2 contain motifs that interact with immune signaling proteins, however more evidence is needed to support this hypothesis. TurboID is a biotin ligase that biotinylates proteins within a 10nm radius. Split-TurboID consists of two functionally inactive fragments of TurboID that within proximity of each other, fuse and actively biotinylate proteins within proximity. We will identify molecular interactors of Kv1.3 channels in mammalian cells using proximity labeling.

METHOD

We fused TurboID or Split-TurboID to the N- or C-terminal Kv1.3 and Kvβ2 using a 15 amino-acid inert linker and transfected the constructs into Hek293 cells. TurboID not fused to Kv1.3 and sham transfection acted as controls. Flow cytometry and patch-clamp electrophysiology confirmed the presence of functional Kv1.3 channels. Biotinylated proteins were streptavidin bead affinity-enriched from cell lysates and confirmed using western blots.

RESULT

Label free quantitation mass spectrometry (LFQ-MS) identified 2,195 biotinylated proteins of which very few were enriched in negative controls. There were 313 proteins as N-term interactors, 385 as C-term interactors, and 226 proteins common to both N and C term fusions, representing proteins indirectly associated with Kv1.3 channels. we identified 14 unique N-term interactors (including metabolic proteins, eg. Naca, Txnl1, Stub1) and 38 unique C-term interactors (including membrane trafficking proteins, eg. Ank3, Plekha7, Erlec1). Split-TurboID interactions between Kv1.3 and Kvβ2 indicate that these interacting proteins are largely dependent on the fully functional Kv1.3 with the Kvβ2 subunit present. We packaged these plasmids into lentiviruses to transduce into mouse microglial cell lines.

CONCLUSION

Our findings indicate Kv1.3 channels interacting with Kvβ2 are a novel molecular mechanism of immune regulation in mammalian cells.

Identification of state-specific proteomic characteristics of microglia-derived exosomes

BACKGROUND

Alzheimer's disease (AD) is the most common neurodegenerative disorder defined by progressive pathological protein aggregation (amyloid-beta and tau) and deterioration of cognitive function. Microglia-mediated neuroinflammation is a key pathological component of AD; however, there are critical gaps in our understanding of how microglia perpetuate AD pathology. One proposed mechanism of microglia-mediated neuroinflammation and neurodegeneration is exosome release because of their critical role in the transport of macromolecules between cells to facilitate intercellular communication. Thus, it is possible that microglia-derived exosomes transfer pathogenic cargo which could perpetuate AD pathology. The proteomic profiles and influence of different microglia-derived exosomal populations on AD pathology remain unknown. We hypothesize that different microglia states determine the molecular composition of exosomes.

METHOD

We treated a murine microglia cell line, BV2 cells, with various cytokines to polarize them and collect their exosomes for downstream mass spectrometry (MS) analyses. Three groups of BV2 cells (n=4/group) were treated with either lipopolysaccharide (LPS) to polarize to a pro-inflammatory state, interleukin 10 (IL-10) to polarize to an anti-inflammatory state, or transforming growth factor beta (TGF-β) to polarize to a homeostatic state. Untreated BV2 cells served as a control group. Following 72 hours of treatment, BV2 cells were lysed and cell culture media was collected for exosome isolation.

RESULT

Transmission electron microscopy images and western blotting for exosomal marker, CD9, confirmed exosome purification by our isolation method. In MS studies, we identified 533 proteins in exosome fractions and 1,866 proteins in BV2 cell proteomes. We found that known exosome related proteins, Sdcbp and Igsf8, were significantly increased in the exosomal proteome compared to the whole cell proteome. We identified proteins that are differentially expressed across polarization with unique proteins increased in exosomes derived from LPS, IL-10, and TGF-β treated BV2 cells. Validation studies of these top hits are ongoing, and studies are underway to replicate these findings in primary microglia.

CONCLUSION

Our results indicate that exosomes derived from microglia adopt distinct state-associated protein profiles which may have differential effects on other cell types. This work will guide future studies concerning the role of exosomal cargo in perpetuating AD pathology.

Cellular proteomic profiling using proximity labeling by TurboID in microglial and neuronal cell lines

BACKGROUND

Despite advancements in systems-level analyses to Alzheimer's disease, global proteomic profiling of brain homogenate cannot resolve molecular changes occurring in distinct cell types. Proximity labeling of proteins by the biotin-ligase TurboID, coupled with mass spectrometry (MS) analyses of biotinylated proteins, can resolve cell-type specific proteomes from brain without cell type enrichment. Before in-vivo applications, it is important to identify proteins preferentially labeled by TurboID in mammalian cells, and directly compare biotinylated proteomes with whole cell proteomes. We determined whether TurboID-labeled proteomes in microglial (BV2) and neuronal (N2A) cell lines are representative of total cellular proteomes under homeostatic and activated conditions.

METHOD

We generated N2A and BV2 cell lines that stably express TurboID fused to a nuclear export sequence. Cells incubated in 200μM biotin and 1μg/mL lipopolysaccharide (LPS) for 48hrs to mimic inflammatory stress. Western blotting and label-free quantitation MS identified biotinylated proteins in whole-cell-lysates and streptavidin-enriched preparations.

RESULT

Western-blot confirmed robust biotinylation in TurboID N2A and BV2 cell-lines. LFQ-MS quantified >3,000 proteins in inputs and >2,400 proteins in biotinylated proteomes from both cell types. In BV2 and N2A inputs, TurboID expression and biotinylation didn't impact the proteome, evidenced by few differentially-expressed proteins and absence of cellular respiration measures in mitochondrial stress-tests, comparing TurboID and non-TurboID cells. Of all the proteins quantified in BV2 and N2A TurboID inputs, ∼50% were also quantified in the biotinylated proteomes in both cell types. Compared to input proteomes of both cell types, the biotinylated proteome was enriched in vesicular, ribosomal, mitochondrial, cytoplasmic and cytoskeletal proteins. The biotinylated proteome successfully differentiated BV2 and N2A cells. LPS stimulation altered levels of 759 proteins in BV2 cells in the input proteome, of which the top increased (e.g. Irg1, Oasl1, Cyb5a) and decreased (e.g. Mrc1, Mgl2, Arg1) proteins showed concordant changes in the biotinylated BV2 proteome.

CONCLUSION

Our analyses show that proteomic labeling by TurboID in microglial and neuronal cell lines doesn't disrupt cellular function. The resulting biotinylated proteomes are reasonably representative of the whole-cell proteome and captures the most robust alterations induced by immune stimuli in microglia. These foundational data will guide future applications of proximity-labeling for cell-type-specific proteomics in-vivo.

Prognostic Scores for Large Vessel Occlusion Strokes

PURPOSE OF THE REVIEW

Endovascular thrombectomy (EVT) for large vessel occlusion strokes (LVOS) presents several treatment challenges. We provide a summary of existing tools for patient selection (pre-EVT tools) and for prognostication of long-term outcomes following reperfusion therapy (post-EVT tools).

RECENT FINDINGS

Recently published randomized trials demonstrated superiority of EVT over medical therapy alone for LVOS. Uniform patient selection paradigms based on demographic, clinical, and radiographic variables are not completely standardized, leading to variability in patient selection for EVT for LVOS. Post-EVT, an accurate assessment of long-term prognosis is critical in the decision-making process.

SUMMARY

Prognostic scores can serve as useful adjuncts to facilitate clinical decision-making during early management of patients with ischemic stroke, particularly those with LVOS. The acute management of LVOS comprises rapid clinical assessment, triage, and cerebrovascular imaging, followed by evaluation for candidacy for thrombolysis and EVT. Pre-EVT prognostic tools that accurately predict the likelihood of benefit from EVT may guide reliable, efficient, and cost-effective patient selection. Following EVT, severe stroke deficits and subacute poststroke complications that portend a poor prognosis may warrant invasive therapies. Clinical decisions regarding these treatment options involve careful discussions between providers and patient families, and are also based on prognosis provided by the treating clinician. Reliable post-EVT prognostic tools can facilitate this by providing accurate and objective prognostic information. Several prognostic tools have been developed and validated in the literature, some of which may be applicable in the pre-EVT and post-EVT settings, although clinical utility and application varies. Validation in contemporary datasets as well as implementation and impact studies are needed before these scales can be used to guide clinical decisions for individual patients.

Anticoagulation Therapy Reduces Recurrent Stroke in Embolic Stroke of Undetermined Source Patients With Elevated Coagulation Markers or Severe Left Atrial Enlargement

Background: The objective of this study was to evaluate if anticoagulation therapy reduces recurrent stroke in embolic stroke of undetermined source (ESUS) patients with left atrial enlargement (LAE) or abnormal markers of coagulation and hemostatic activity (MOCHA) compared to antiplatelet therapy.

Methods: ESUS patients from January 1, 2017, to June 30, 2019, underwent outpatient cardiac monitoring and the MOCHA profile (serum d-dimer, prothrombin fragment 1.2, thrombin–antithrombin complex, and fibrin monomer). Anticoagulation was offered to patients with abnormal MOCHA (≥2 elevated markers) or left atrial volume index 40 mL/m². Patients were evaluated for recurrent stroke or major hemorrhage at routine clinical follow-up. We compared this patient cohort (cohort 2) to a historical cohort (cohort 1) who underwent the same protocol but remained on antiplatelet therapy.

Results: Baseline characteristics in cohort 2 (n = 196; mean age = 63 ± 16 years, 59% female, 49% non-White) were similar to cohort 1 (n = 42) except that cohort 2 had less diabetes (43 vs. 24%, p = 0.01) and more tobacco use (26 vs. 43%, p = 0.04). Overall, 45 patients (23%) in cohort 2 initiated anticoagulation based on abnormal MOCHA or LAE. During mean follow-up of 13 ± 10 months, cohort 2 had significantly lower recurrent stroke rates than cohort 1 (14 vs. 3%, p = 0.009) with no major hemorrhages.

Conclusions: Anticoagulation therapy in a subgroup of ESUS patients with abnormal MOCHA or severe LAE may be associated with a reduced rate of recurrent stroke compared to antiplatelet therapy. A prospective, randomized study is warranted to validate these results.

Cerebrovascular events and outcomes in hospitalized patients with COVID-19: The SVIN COVID-19 Multinational Registry

BACKGROUND

Severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) has been associated with a significant risk of thrombotic events in critically ill patients.

AIM

To summarize the findings of a multinational observational cohort of patients with SARS-CoV-2 and cerebrovascular disease.

METHODS

Retrospective observational cohort of consecutive adults evaluated in the emergency department and/or admitted with coronavirus disease 2019 (COVID-19) across 31 hospitals in four countries (1 February 2020-16 June 2020). The primary outcome was the incidence rate of cerebrovascular events, inclusive of acute ischemic stroke, intracranial hemorrhages (ICH), and cortical vein and/or sinus thrombosis (CVST).

RESULTS

Of the 14,483 patients with laboratory-confirmed SARS-CoV-2, 172 were diagnosed with an acute cerebrovascular event (1.13% of cohort; 1130/100,000 patients, 95%CI 970-1320/100,000), 68/171 (40.5%) were female and 96/172 (55.8%) were between the ages 60 and 79 years. Of these, 156 had acute ischemic stroke (1.08%; 1080/100,000 95%CI 920-1260/100,000), 28 ICH (0.19%; 190/100,000 95%CI 130-280/100,000), and 3 with CVST (0.02%; 20/100,000, 95%CI 4-60/100,000). The in-hospital mortality rate for SARS-CoV-2-associated stroke was 38.1% and for ICH 58.3%. After adjusting for clustering by site and age, baseline stroke severity, and all predictors of in-hospital mortality found in univariate regression (p < 0.1: male sex, tobacco use, arrival by emergency medical services, lower platelet and lymphocyte counts, and intracranial occlusion), cryptogenic stroke mechanism (aOR 5.01, 95%CI 1.63-15.44, p < 0.01), older age (aOR 1.78, 95%CI 1.07-2.94, p = 0.03), and lower lymphocyte count on admission (aOR 0.58, 95%CI 0.34-0.98, p = 0.04) were the only independent predictors of mortality among patients with stroke and COVID-19.

CONCLUSIONS

COVID-19 is associated with a small but significant risk of clinically relevant cerebrovascular events, particularly ischemic stroke. The mortality rate is high for COVID-19-associated cerebrovascular complications; therefore, aggressive monitoring and early intervention should be pursued to mitigate poor outcomes.

Validation of an admission coagulation panel for risk stratification of COVID-19 patients

BACKGROUND

There is limited data on the markers of coagulation and hemostatic activation (MOCHA) profile in Coronavirus disease 2019 (COVID-19) and its ability to identify COVID-19 patients at risk for thrombotic events and other complications.

METHODS

Hospitalized patients with confirmed SARS-COV-2 from four Atlanta hospitals were included in this observational cohort study and underwent admission testing of MOCHA parameters (plasma d-dimer, prothrombin fragment 1.2, thrombin-antithrombin complex, fibrin monomer). Clinical outcomes included deep vein thrombosis, pulmonary embolism, myocardial infarction, ischemic stroke, access line thrombosis, ICU admission, intubation and mortality.

MAIN RESULTS

Of 276 patients (mean age 59 ± 6.4 years, 47% female, 62% African American), 45 (16%) had a thrombotic endpoint. Each MOCHA parameter was independently associated with a thrombotic event (p<0.05) and ≥ 2 abnormalities was associated with thrombotic endpoints (OR 3.3, 95% CI 1.2-8.8) as were admission D-dimer ≥ 2000 ng/mL (OR 3.1, 95% CI 1.5-6.6) and ≥ 3000 ng/mL (OR 3.6, 95% CI 1.6-7.9). However, only ≥ 2 MOCHA abnormalities were associated with ICU admission (OR 3.0, 95% CI 1.7-5.2) and intubation (OR 3.2, 95% CI 1.6-6.4). MOCHA and D-dimer cutoffs were not associated with mortality. MOCHA with <2 abnormalities (26% of the cohort) had 89% sensitivity and 93% negative predictive value for a thrombotic endpoint.

CONCLUSIONS

An admission MOCHA profile is useful to risk-stratify COVID-19 patients for thrombotic complications and more effective than isolated d-dimer for predicting risk of ICU admission and intubation.

Extracellular signal-regulated kinase regulates microglial immune responses in Alzheimer's disease

The importance of mitogen-activated protein kinase (MAPK) pathway signaling in regulating microglia-mediated neuroinflammation in Alzheimer's disease (AD) remains unclear. We examined the role of MAPK signaling in microglia using a preclinical model of AD pathology and quantitative proteomics studies of postmortem human brains. In multiplex immunoassay analyses of MAPK phosphoproteins in acutely isolated microglia and brain tissue from 5xFAD mice, we found phosphorylated extracellular signal-regulated kinase (ERK) was the most strongly upregulated phosphoprotein within the MAPK pathway in acutely isolated microglia, but not whole-brain tissue from 5xFAD mice. The importance of ERK signaling in primary microglia cultures was next investigated using transcriptomic profiling and functional assays of amyloid-β and neuronal phagocytosis, which confirmed that ERK is a critical regulator of IFNγ-mediated pro-inflammatory activation of microglia, although it was also partly important for constitutive microglial functions. Phospho-ERK was an upstream regulator of disease-associated microglial gene expression (Trem2, Tyrobp), as well as several human AD risk genes (Bin1, Cd33, Trem2, Cnn2), indicative of the importance of microglial ERK signaling in AD pathology. Quantitative proteomic analyses of postmortem human brain showed that ERK1 and ERK2 were the only MAPK proteins with increased protein expression and positive associations with neuropathological grade. In a human brain phosphoproteomic study, we found evidence for increased flux through the ERK signaling pathway in AD. Overall, our analyses strongly suggest that ERK phosphorylation, particularly in microglia in mouse models, is a regulator of pro-inflammatory immune responses in AD pathogenesis.

Kv1.3 modulates neuroinflammation and neurodegeneration in Parkinson's disease

Characterization of the key cellular targets contributing to sustained microglial activation in neurodegenerative diseases, including Parkinson's disease (PD), and optimal modulation of these targets can provide potential treatments to halt disease progression. Here, we demonstrated that microglial Kv1.3, a voltage-gated potassium channel, was transcriptionally upregulated in response to aggregated α-synuclein (αSynAgg) stimulation in primary microglial cultures and animal models of PD, as well as in postmortem human PD brains. Patch-clamp electrophysiological studies confirmed that the observed Kv1.3 upregulation translated to increased Kv1.3 channel activity. The kinase Fyn, a risk factor for PD, modulated transcriptional upregulation and posttranslational modification of microglial Kv1.3. Multiple state-of-the-art analyses, including Duolink proximity ligation assay imaging, revealed that Fyn directly bound to Kv1.3 and posttranslationally modified its channel activity. Furthermore, we demonstrated the functional relevance of Kv1.3 in augmenting the neuroinflammatory response by using Kv1.3-KO primary microglia and the Kv1.3-specific small-molecule inhibitor PAP-1, thus highlighting the importance of Kv1.3 in neuroinflammation. Administration of PAP-1 significantly inhibited neurodegeneration and neuroinflammation in multiple animal models of PD. Collectively, our results imply that Fyn-dependent regulation of Kv1.3 channels plays an obligatory role in accentuating the neuroinflammatory response in PD and identify Kv1.3 as a potential therapeutic target for PD.

Clinical Outcomes of Critically III Patients with COVID-19 by Race

Background

Studies of COVID-19 have shown that African Americans have been affected by the virus at a higher rate compared to other races. This cohort study investigated comorbidities and clinical outcomes by race among COVID-19 patients admitted to the intensive care unit.

Methods

This is a case series of critically ill patients admitted with COVID-19 to an academic healthcare system in Atlanta, Georgia. The study included all critically ill hospitalized patients between March 6, 2020, and May 5, 2020. Clinical outcomes during hospitalization included mechanical ventilation, renal replacement therapy, and mortality stratified by race.

Results

Of 288 patients included (mean age, 63 ± 16 years; 45% female), 210 (73%) were African American. African Americans had significantly higher rates of comorbidities compared to other races, including hypertension (80% vs 59%, P = 0.001), diabetes (49% vs 34%, P = 0.026), and mean BMI (33 kg/m² vs 28 kg/m², P < 0.001). Despite African Americans requiring continuous renal replacement therapy during hospitalization at higher rates than other races (27% vs 13%, P = 0.011), rates of intubation, intensive care unit length of stay, and overall mortality (30% vs 24%, P = 0.307) were similar.

Conclusion

This racially diverse series of critically ill COVID-19 patients shows that despite higher rates of comorbidities at hospital admission in African Americans compared with other races, there was no significant difference in mortality.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40615-021-00966-0.

The Utility of the Markers of Coagulation and Hemostatic Activation Profile in the Management of Embolic Strokes of Undetermined Source

BACKGROUND

Potential causes of embolic stroke of undetermined source (ESUS) include occult malignancy, venous thrombosis (VTE) with paradoxical embolism, and hypercoagulable disorders. Given the association of markers of coagulation and hemostatic activation (MOCHA) with these causes, the objective of this study was to validate the utility of the MOCHA profile in identifying the underlying cause of stroke.

METHODS

We prospectively identified ESUS patients from January 1, 2017 to December 1, 2019 who underwent MOCHA profile (plasma d-dimer, prothrombin fragment 1.2, thrombin-antithrombin complex, fibrin monomer) testing. Abnormal MOCHA profile was defined as ≥ 2 abnormal markers. New diagnoses of malignancy, VTE, hypercoagulable disorders and recurrent stroke were identified during routine clinical follow-up.

RESULTS

Of 236 ESUS patients, 104 (44%) patients had an abnormal MOCHA profile. In multivariable analyses the number of MOCHA abnormalities was significantly associated with malignancy, VTE, and hypercoagulable disorders (OR 2.59, CI 95% 1.78-3.76, p<0.001). Sensitivity, specificity, positive predictive value, and negative predictive value of an abnormal MOCHA profile for the combined outcome of malignancy, VTE, and hypercoagulability was 96%, 62%, 23%, and 99% respectively.

DISCUSSION

The MOCHA profile was able to identify ESUS patients more likely to have malignancy, VTE, and hypercoagulable disorders during follow-up. Our results show that a normal MOCHA profile in ESUS patients can effectively rule out these potential causes of ESUS.

Systems-based proteomics to resolve the biology of Alzheimer's disease beyond amyloid and tau

The repeated failures of amyloid-targeting therapies have challenged our narrow understanding of Alzheimer's disease (AD) pathogenesis and inspired wide-ranging investigations into the underlying mechanisms of disease. Increasing evidence indicates that AD develops from an intricate web of biochemical and cellular processes that extend far beyond amyloid and tau accumulation. This growing recognition surrounding the diversity of AD pathophysiology underscores the need for holistic systems-based approaches to explore AD pathogenesis. Here we describe how network-based proteomics has emerged as a powerful tool and how its application to the AD brain has provided an informative framework for the complex protein pathophysiology underlying the disease. Furthermore, we outline how the AD brain network proteome can be leveraged to advance additional scientific and translational efforts, including the discovery of novel protein biomarkers of disease.

Comparative proteomic analysis highlights metabolic dysfunction in α-synucleinopathy

The synaptic protein α-synuclein is linked through genetics and neuropathology to the pathogenesis of Parkinson’s disease and related disorders. However, the mechanisms by which α-synuclein influences disease onset and progression are incompletely understood. To identify pathogenic pathways and therapeutic targets we performed proteomic analysis in a highly penetrant new Drosophila model of α-synucleinopathy. We identified 476 significantly upregulated and 563 significantly downregulated proteins in heads from α-synucleinopathy model flies compared to controls. We then used multiple complementary analyses to identify and prioritize genes and pathways within the large set of differentially expressed proteins for functional studies. We performed Gene Ontology enrichment analysis, integrated our proteomic changes with human Parkinson’s disease genetic studies, and compared the α-synucleinopathy proteome with that of tauopathy model flies, which are relevant to Alzheimer’s disease and related disorders. These approaches identified GTP cyclohydrolase (GCH1) and folate metabolism as candidate mediators of α-synuclein neurotoxicity. In functional validation studies, we found that the knockdown of Drosophila Gch1 enhanced locomotor deficits in α-synuclein transgenic flies, while folate supplementation protected from α-synuclein toxicity. Our integrative analysis suggested that mitochondrial dysfunction was a common downstream mediator of neurodegeneration. Accordingly, Gch1 knockdown enhanced metabolic dysfunction in α-synuclein transgenic fly brains while folate supplementation partially normalized brain bioenergetics. Here we outline and implement an integrative approach to identify and validate potential therapeutic pathways using comparative proteomics and genetics and capitalizing on the facile genetic and pharmacological tools available in Drosophila.

C-Reactive protein as a prognostic indicator in hospitalized patients with COVID-19

Recent studies have reported that CRP levels are elevated in patients with COVID-19 and may correlate with severity of disease and disease progression. We conducted a retrospective cohort analysis of the medical records of 268 adult patients, who were admitted to one of the six cohorted COVID ICUs across Emory Healthcare System and had at least two CRP values within the first seven days of admission to study the temporal progression of CRP and its association with all-cause in-hospital mortality. The median CRP during hospitalization for the entire cohort was 130 mg/L (IQR 82–191 mg/L), and the median CRP on ICU admission was 169 (IQR 111–234). The hospitalization-wide median CRP was significantly higher amongst the patients who died, compared to those who survived [206 mg/L (157–288 mg/L) vs 114 mg/L (72–160 mg/L), p<0.001]. CRP levels increased in a linear fashion during the first week of hospitalization and peaked on day 5. Compared to patients who died, those who survived had lower peak CRP levels and earlier declines. CRP levels were significantly higher in patients who died compared to those who survived (p<0.001). Our findings support the utility of daily CRP values in hospitalized COVID-19 patients and provide early thresholds during hospitalization that may facilitate risk stratification and prognostication.

Trends and diagnostic value of D-dimer levels in patients hospitalized with coronavirus disease 2019

Coronavirus disease 2019 (COVID-19) has been associated with increased incidence of venous thromboembolic events (VTE) as well as mortality. D-dimer is a marker of fibrinolysis and has been used as a diagnostic and prognostic marker in VTE among other diseases. The purpose of our study is to describe outcomes from out center and to examine trends in D-dimer levels as it relates to VTE and mortality.Patients admitted with confirmed COVID-19 cases to Emory Healthcare from March 12, 2020 through April 6, 2020 with measured plasma D-dimer levels were included in our retrospective analysis. Relevant data about comorbidities, hospitalization course, laboratory results, and outcomes were analyzed.One hundred fifteen patients were included in our study. Mean age was 64 ± 15 years, 47 (41%) females and 84 (73%) African-American. Hypertension was present in 83 (72%) and diabetes in 60 (52%). Mean duration of hospitalization was 19 ± 11 days with 62 (54%) patients intubated (mean duration of 13 ± 8 days). VTE was diagnosed in 27 (23%) patients (mean time to diagnosis 14 ± 9 days). Median D-dimer within the first 7 days of hospitalization was higher (6450 vs. 1596 ng/mL, p < 0.001) in VTE cases compared to non-VTE cases, and was predictive of VTE (area under the curve [AUC] = 0.72, optimal threshold 2500 ng/mL) although not of mortality (AUC 0.55, P = .34). Change in D-dimer level (AUC = 0.72 P = .004) and rate of D-dimer rise (AUC = 0.75 P = .001) were also predictive of VTE, though neither predicted death (P > .05 for all). Within the first 7 days of hospitalization, peak D-dimer level of >2500 ng/mL and a rate of change exceeding 150 ng/mL/d were predictive of future diagnosis of VTE. Rise in D-dimer >2000 ng/mL within any 24 hour period through hospital day 10 had 75% sensitivity and 74% specificity for diagnosis of VTE.We found that both magnitude and rate of rise in d-dimer within the first 10 days of hospitalization are predictive of diagnosis of VTE but not mortality. These parameters may aid in identifying individuals with possible underlying VTE or at high risk for VTE, thereby guiding risk stratification and anticoagulation policies in COVID-19 patients.

Ischemic stroke in COVID-19: An urgent need for early identification and management

OBJECTIVE

In the setting of the Coronavirus Disease 2019 (COVID-19) global pandemic caused by SARS-CoV-2, a potential association of this disease with stroke has been suggested. We aimed to describe the characteristics of patients who were admitted with COVID-19 and had an acute ischemic stroke (AIS).

METHODS

This is a case series of PCR-confirmed COVID-19 patients with ischemic stroke admitted to an academic health system in metropolitan Atlanta, Georgia (USA) between March 24th, 2020 and July 17th, 2020. Demographic, clinical, and radiographic characteristics were described.

RESULTS

Of 396 ischemic stroke patients admitted during this study period, 13 (2.5%) were also diagnosed with COVID-19. The mean age of patients was 61.6 ± 10.8 years, 10 (76.9%) male, 8 (61.5%) were Black Americans, mean time from last normal was 4.97 ± 5.1 days, and only one received acute reperfusion therapy. All 13 patients had at least one stroke-associated co-morbidity. The predominant pattern of ischemic stroke was embolic with 4 explained by atrial fibrillation. COVID-19 patients had a significantly higher rate of cryptogenic stroke than non-COVID-19 patients during the study period (69% vs 17%, p = 0.0001).

CONCLUSIONS

In our case series, ischemic stroke affected COVID-19 patients with traditional stroke risk factors at an age typically seen in non-COVID populations, and mainly affecting males and Black Americans. We observed a predominantly embolic pattern of stroke with a higher than expected rate of cryptogenic strokes, a prolonged median time to presentation and symptom recognition limiting the use of acute reperfusion treatments. These results highlight the need for increased community awareness, early identification, and management of AIS in COVID-19 patients.

Hyperdense vessel sign as a potential guide for the choice of stent retriever versus contact aspiration as first-line thrombectomy strategy

BACKGROUND

The first-pass effect (FPE) has emerged as a key metric for efficacy in mechanical thrombectomy (MT). The hyperdense vessel sign (HDVS) on non-contrast head CT (NCCT) indicates a higher clot content of red blood cells.

OBJECTIVE

To assess whether the HDVS could serve as an imaging biomarker for guiding first-line device selection in MT.

METHODS

A prospective MT database was reviewed for consecutive patients with anterior circulation large vessel occlusion stroke who underwent thrombectomy with stent retriever (SR) or contact aspiration (CA) as first-line therapy between January 2012 and November 2018. Pretreatment NCCT scans were evaluated for the presence of HDVS. The primary outcome was FPE (modified Thrombolysis in Cerebral Infarction score 2c/3). The primary analysis was the interaction between HDVS and thrombectomy modality on FPE. Secondary analyses aimed to evaluate the predictors of FPE.

RESULTS

A total of 779 patients qualified for the analysis. HDVS and FPE were reported in 473 (60.7%) and 286 (36.7%) patients, respectively. The presence of HDVS significantly modified the effect of thrombectomy modality on FPE (p=0.01), with patients with HDVS having a significantly higher rate of FPE with a SR (41.3% vs 22.2%, p=0.001; adjusted OR 2.11 (95% CI 1.20 to 3.70), p=0.009) and non-HDVS patients having a numerically better response to CA (41.4% vs 33.9%, p=0.28; adjusted OR 0.58 (95% CI 0.311 to 1.084), p=0.088). Age (OR 1.01 (95% CI 1.00 to 1.02), p=0.04) and balloon guide catheter (OR 2.08 (95% CI 1.24 to 3.47), p=0.005) were independent predictors of FPE in the overall population.

CONCLUSION

Our data suggest that patients with HDVS may have a better response to SRs than CA for the FPE. Larger confirmatory prospective studies are warranted.

Predicting outcomes after acute reperfusion therapy for basilar artery occlusion

BACKGROUND AND PURPOSE

Basilar artery occlusion (BAO) leads to high rates of morbidity and mortality, despite successful recanalization. The discordance between flow restoration and long-term functional status clouds clinical decision-making regarding further aggressive care. We sought to develop and validate a practical, prognostic tool for the prediction of 3-month favorable outcome after acute reperfusion therapy for BAO.

METHODS

This retrospective, multicenter, observational study was conducted at four high-volume stroke centers in the USA and Europe. Multivariate regression analysis was performed to identify predictors of favorable outcome (90-day modified Rankin scale scores 0-2) and derive a clinically applicable prognostic model (the Pittsburgh Outcomes after Stroke Thrombectomy-Vertebrobasilar (POST-VB) score). The POST-VB score was evaluated and internally validated with regard to calibration and discriminatory ability. External validity was assessed in patient cohorts at three separate centers.

RESULTS

In the derivation cohort of 59 patients, independent predictors of favorable outcome included smaller brainstem infarct volume on post-procedure magnetic resonance imaging (P < 0.01) and younger age (P = 0.01). POST-VB score was calculated as: age + (10 × brainstem infarct volume). POST-VB score demonstrated excellent discriminatory ability [area under the receiver-operating characteristic curve (AUC) = 0.91] and adequate calibration (P = 0.88) in the derivation cohort (Center A). It performed equally well across the three external validation cohorts (Center B, AUC = 0.89; Center C, AUC = 0.78; Center D, AUC = 0.80). Overall, a POST-VB score < 49 was associated with an 88% likelihood of favorable outcome, as compared to 4% with a score ≥ 125.

CONCLUSIONS

The POST-VB score effectively predicts 3-month functional outcome following acute reperfusion therapy for BAO and may aid in guiding post-procedural care.

Flow Cytometry Approach to Characterize Phagocytic Properties of Acutely-Isolated Adult Microglia and Brain Macrophages In Vitro

Microglia and central nervous system (CNS)-infiltrating macrophages, collectively called CNS mononuclear phagocytes (CNS-MPs), play central roles in neurological diseases including neurodegeneration and stroke. CNS-MPs are involved in phagocytic clearance of pathological proteins, debris and neuronal synapses, each with distinct underlying molecular pathways. Characterizing these phagocytic properties can provide a functional readout that compliments molecular profiling of microglia using traditional flow cytometry, transcriptomics and proteomics approaches. Phagocytic profiling of microglia has relied on microscopic visualization and in vitro cultures of mouse neonatal microglia. The former approach suffers from limited sampling while the latter approach is inherently poorly reflective of the true in vivo state of adult CNS-MPs. This paper describes optimized protocols to phenotype phagocytic properties of acutely-isolated mouse CNS-MPs by flow cytometry. CNS-MPs are acutely isolated from adult mouse brain using mechanical dissociation followed by density gradient centrifugation, incubated with fluorescent microspheres or fluorescent Aβ fibrils, washed, and then labeled with panels of antibodies against surface markers (CD11b, CD45). Using this approach, it is possible to compare phagocytic properties of brain-resident microglia with CNS-infiltrating macrophages and then assess the effect of aging and disease pathology on these phagocytic phenotypes. This rapid method also holds potential to functionally phenotype acutely-isolated human CNS-MPs from post-mortem or surgical brain specimens. Additionally, specific mechanisms of phagocytosis by CNS-MP subsets can be investigated by inhibiting select phagocytic pathways.

Flow-cytometric microglial sorting coupled with quantitative proteomics identifies moesin as a highly-abundant microglial protein with relevance to Alzheimer's disease

BACKGROUND

Proteomic characterization of microglia provides the most proximate assessment of functionally relevant molecular mechanisms of neuroinflammation. However, microglial proteomics studies have been limited by low cellular yield and contamination by non-microglial proteins using existing enrichment strategies.

METHODS

We coupled magnetic-activated cell sorting (MACS) and fluorescence activated cell sorting (FACS) of microglia with tandem mass tag-mass spectrometry (TMT-MS) to obtain a highly-pure microglial proteome and identified a core set of highly-abundant microglial proteins in adult mouse brain. We interrogated existing human proteomic data for Alzheimer's disease (AD) relevance of highly-abundant microglial proteins and performed immuno-histochemical and in-vitro validation studies.

RESULTS

Quantitative multiplexed proteomics by TMT-MS of CD11b + MACS-enriched (N = 5 mice) and FACS-isolated (N = 5 mice), from adult wild-type mice, identified 1791 proteins. A total of 203 proteins were highly abundant in both datasets, representing a core-set of highly abundant microglial proteins. In addition, we found 953 differentially enriched proteins comparing MACS and FACS-based approaches, indicating significant differences between both strategies. The FACS-isolated microglia proteome was enriched with cytosolic, endoplasmic reticulum, and ribosomal proteins involved in protein metabolism and immune system functions, as well as an abundance of canonical microglial proteins. Conversely, the MACS-enriched microglia proteome was enriched with mitochondrial and synaptic proteins and higher abundance of neuronal, oligodendrocytic and astrocytic proteins. From the 203 consensus microglial proteins with high abundance in both datasets, we confirmed microglial expression of moesin (Msn) in wild-type and 5xFAD mouse brains as well as in human AD brains. Msn expression is nearly exclusively found in microglia that surround Aβ plaques in 5xFAD brains. In in-vitro primary microglial studies, Msn silencing by siRNA decreased Aβ phagocytosis and increased lipopolysaccharide-induced production of the pro-inflammatory cytokine, tumor necrosis factor (TNF). In network analysis of human brain proteomic data, Msn was a hub protein of an inflammatory co-expression module positively associated with AD neuropathological features and cognitive dysfunction.

CONCLUSIONS

Using FACS coupled with TMT-MS as the method of choice for microglial proteomics, we define a core set of highly-abundant adult microglial proteins. Among these, we validate Msn as highly-abundant in plaque-associated microglia with relevance to human AD.

Markers of coagulation and hemostatic activation aid in identifying causes of cryptogenic stroke

OBJECTIVE

To test the hypothesis that markers of coagulation and hemostatic activation (MOCHA) help identify causes of cryptogenic stroke, we obtained serum measurements on 132 patients and followed them up to identify causes of stroke.

METHODS

Consecutive patients with cryptogenic stroke who met embolic stroke of undetermined source (ESUS) criteria from January 1, 2017, to October 31, 2018, underwent outpatient cardiac monitoring and the MOCHA profile (serum D-dimer, prothrombin fragment 1.2, thrombin-antithrombin complex, and fibrin monomer) obtained ≥2 weeks after the index stroke; abnormal MOCHA profile was defined as ≥2 elevated markers. Prespecified endpoints monitored during routine clinical visits included new atrial fibrillation (AF), malignancy, venous thromboembolism (VTE), or other defined hypercoagulable states (HS).

RESULTS

Overall, 132 patients with ESUS (mean age 64 ± 15 years, 61% female, 51% nonwhite) met study criteria. During a median follow-up of 10 (interquartile range 7-14) months, AF, malignancy, VTE, or HS was identified in 31 (23%) patients; the 53 (40%) patients with ESUS with abnormal MOCHA were significantly more likely than patients with normal levels to have subsequent new diagnoses of malignancy (21% vs 0%, p < 0.001), VTE (9% vs 0%, p = 0.009), or HS (11% vs 0%, p = 0.004) but not AF (8% vs 9%, p = 0.79). The combination of 4 normal MOCHA and normal left atrial size (n = 30) had 100% sensitivity for ruling out the prespecified endpoints.

CONCLUSION

The MOCHA profile identified patients with cryptogenic stroke more likely to have new malignancy, VTE, or HS during short-term follow-up and may be useful in direct evaluation for underlying causes of cryptogenic stroke.

Large-scale proteomic analysis of Alzheimer's disease brain and cerebrospinal fluid reveals early changes in energy metabolism associated with microglia and astrocyte activation

Our understanding of Alzheimer's disease (AD) pathophysiology remains incomplete. Here we used quantitative mass spectrometry and coexpression network analysis to conduct the largest proteomic study thus far on AD. A protein network module linked to sugar metabolism emerged as one of the modules most significantly associated with AD pathology and cognitive impairment. This module was enriched in AD genetic risk factors and in microglia and astrocyte protein markers associated with an anti-inflammatory state, suggesting that the biological functions it represents serve a protective role in AD. Proteins from this module were elevated in cerebrospinal fluid in early stages of the disease. In this study of >2,000 brains and nearly 400 cerebrospinal fluid samples by quantitative proteomics, we identify proteins and biological processes in AD brains that may serve as therapeutic targets and fluid biomarkers for the disease.