Targeting myeloperoxidase to reduce neuroinflammation in X-linked dystonia parkinsonism.

Although the genetic locus of X-linked dystonia parkinsonism (XDP), a neurodegenerative disease endemic in the Philippines, is well-characterized, the exact molecular mechanisms leading to neuronal loss are not yet fully understood. Recently, we demonstrated a significant increase in astrogliosis and microgliosis together with an increase in myeloperoxidase (MPO) levels in XDP post-mortem prefrontal cortex (PFC), suggesting a role for neuroinflammation in XDP pathogenesis. Here, we demonstrated a significant increase in MPO activity in XDP PFC using a novel specific MPO-activatable fluorescent agent (MAFA). Additionally, we demonstrated a significant increase in reactive oxygen species (ROS) in XDP-derived fibroblasts as well as in SH-SY5Y cells treated with post-mortem XDP PFC, further supporting a role for MPO in XDP. To determine whether increases in MPO activity were linked to increases in ROS, MPO content was immuno-depleted from XDP PFC [MPO(-)], which resulted in a significant decrease in ROS in SH-SY5Y cells. Consistently, the treatment with verdiperstat, a potent and selective MPO inhibitor, significantly decreased ROS in both XDP-derived fibroblasts and XDP PFC-treated SH-SY5Y cells. Collectively, our results suggest that MPO inhibition mitigates oxidative stress and may provide a novel therapeutic strategy for XDP treatment. Highlights: MPO activity is increased in XDP post-mortem prefrontal cortex.MPO activity is increased in cellular models of XDP.MPO increases reactive oxygen species (ROS) in vitro.Inhibiting MPO mitigates ROS in XDP.The MPO inhibitor, verdiperstat, dampens ROS suggesting a potential therapeutic strategy for XDP.

Therapeutic potential of exercise-hormone irisin in Alzheimer's disease.

ABSTRACT: Irisin is a myokine that is generated by cleavage of the membrane protein fibronectin type III domain-containing protein 5 (FNDC5) in response to physical exercise. Studies reveal that irisin/FNDC5 has neuroprotective functions against Alzheimer's disease, the most common form of dementia in the elderly, by improving cognitive function and reducing amyloid-ß and tau pathologies as well as neuroinflammation in cell culture or animal models of Alzheimer's disease. Although current and ongoing studies on irisin/FNDC5 show promising results, further mechanistic studies are required to clarify its potential as a meaningful therapeutic target for alleviating Alzheimer's disease. We recently found that irisin treatment reduces amyloid-ß pathology by increasing the activity/levels of amyloid- ß-degrading enzyme neprilysin secreted from astrocytes. Herein, we present an overview of irisin/FNDC5's protective roles and mechanisms against Alzheimer's disease.

Polygenic hazard score models for the prediction of Alzheimer's free survival using the lasso for Cox's proportional hazards model.

The prediction of the susceptibility of an individual to a certain disease is an important and timely research area. An established technique is to estimate the risk of an individual with the help of an integrated risk model, that is, a polygenic risk score with added epidemiological covariates. However, integrated risk models do not capture any time dependence, and may provide a point estimate of the relative risk with respect to a reference population. The aim of this work is twofold. First, we explore and advocate the idea of predicting the time-dependent hazard and survival (defined as disease-free time) of an individual for the onset of a disease. This provides a practitioner with a much more differentiated view of absolute survival as a function of time. Second, to compute the time-dependent risk of an individual, we use published methodology to fit a Cox's proportional hazard model to data from a genetic SNP study of time to Alzheimer's disease (AD) onset, using the lasso to incorporate further epidemiological variables such as sex, APOE (apolipoprotein E, a genetic risk factor for AD) status, 10 leading principal components, and selected genomic loci. We apply the lasso for Cox's proportional hazards to a data set of 6792 AD patients (composed of 4102 cases and 2690 controls) and 87 covariates. We demonstrate that fitting a lasso model for Cox's proportional hazards allows one to obtain more accurate survival curves than with state-of-the-art (likelihood-based) methods. Moreover, the methodology allows one to obtain personalized survival curves for a patient, thus giving a much more differentiated view of the expected progression of a disease than the view offered by integrated risk models. The runtime to compute personalized survival curves is under a minute for the entire data set of AD patients, thus enabling it to handle datasets with 60,000-100,000 subjects in less than 1 h.

Prediction of disease-free survival for precision medicine using cooperative learning on multi-omic data.

In precision medicine, both predicting the disease susceptibility of an individual and forecasting its disease-free survival are areas of key research. Besides the classical epidemiological predictor variables, data from multiple (omic) platforms are increasingly available. To integrate this wealth of information, we propose new methodology to combine both cooperative learning, a recent approach to leverage the predictive power of several datasets, and polygenic hazard score models. Polygenic hazard score models provide a practitioner with a more differentiated view of the predicted disease-free survival than the one given by merely a point estimate, for instance computed with a polygenic risk score. Our aim is to leverage the advantages of cooperative learning for the computation of polygenic hazard score models via Cox's proportional hazard model, thereby improving the prediction of the disease-free survival. In our experimental study, we apply our methodology to forecast the disease-free survival for Alzheimer's disease (AD) using three layers of data. One layer contains epidemiological variables such as sex, APOE (apolipoprotein E, a genetic risk factor for AD) status and 10 leading principal components. Another layer contains selected genomic loci, and the last layer contains methylation data for selected CpG sites. We demonstrate that the survival curves computed via cooperative learning yield an AUC of around $0.7$, above the state-of-the-art performance of its competitors. Importantly, the proposed methodology returns (1) a linear score that can be easily interpreted (in contrast to machine learning approaches), and (2) a weighting of the predictive power of the involved data layers, allowing for an assessment of the importance of each omic (or other) platform. Similarly to polygenic hazard score models, our methodology also allows one to compute individual survival curves for each patient.

Development of a New Positron Emission Tomography Imaging Radioligand Targeting RIPK1 in the Brain and Characterization in Alzheimer's Disease.

Targeting receptor-interacting protein kinase 1 (RIPK1) has emerged as a promising therapeutic stratagem for neurodegenerative disorders, particularly Alzheimer's disease (AD). A positron emission tomography (PET) probe enabling brain RIPK1 imaging can provide a powerful tool to unveil the neuropathology associated with RIPK1. Herein, the development of a new PET radioligand, [11C]CNY-10 is reported, which may enable brain RIPK1 imaging. [11C]CNY-10 is radiosynthesized with a high radiochemical yield (41.8%) and molar activity (305 GBq/µmol). [11C]CNY-10 is characterized by PET imaging in rodents and a non-human primate, demonstrating good brain penetration, binding specificity, and a suitable clearance kinetic profile. It is performed autoradiography of [11C]CNY-10 in human AD and healthy control postmortem brain tissues, which shows strong radiosignal in AD brains higher than healthy controls. Subsequently, it is conducted further characterization of RIPK1 in AD using [11C]CNY-10-based PET studies in combination with immunohistochemistry leveraging the 5xFAD mouse model. It is found that AD mice revealed RIPK1 brain signal significantly higher than WT control mice and that RIPK1 is closely related to amyloid plaques in the brain. The studies enable further translational studies of [11C]CNY-10 for AD and potentially other RIPK1-related human studies.

γ-Secretase Modulator BPN15606 Reduced Aß42 and Aß40 and Countered Alzheimer-Related Pathologies in a Mouse Model of Down Syndrome.

OBJECTIVES: Due to increased gene dose for the amyloid precursor protein (APP), elderly adults with Down syndrome (DS) are at a markedly increased risk of Alzheimer's disease (AD), known as DS-AD. How the increased APP gene dose acts and which APP products are responsible for DS-AD is not well understood, thus limiting strategies to target pathogenesis. As one approach to address this question, we used a novel class of γ-secretase modulators that promote γ-site cleavages by the γ-secretase complex, resulting in lower levels of the Aß42 and Aß40 peptides. METHODS: Ts65Dn mice, which serve as a model of DS, were treated via oral gavage with 10 mg/kg/weekday of BPN15606 (a potent and novel pyridazine-containing γ-secretase modulators). Treatment started at 3 months-of-age and lasted for 4 months. RESULTS: Demonstrating successful target engagement, treatment with BPN15606 significantly decreased levels of Aß40 and Aß42 in the cortex and hippocampus; it had no effect on full-length APP or its C-terminal fragments in either 2 N or Ts65Dn mice. Importantly, the levels of total amyloid-ß were not impacted, pointing to BPN15606-mediated enhancement of processivity of γ-secretase. Additionally, BPN15606 rescued hyperactivation of Rab5, a protein responsible for regulating endosome function, and normalized neurotrophin signaling deficits. BPN15606 treatment also normalized the levels of synaptic proteins and tau phosphorylation, while reducing astrocytosis and microgliosis, and countering cognitive deficits. INTERPRETATION: Our findings point to the involvement of increased levels of Aß42 and/or Aß40 in contributing to several molecular and cognitive traits associated with DS-AD. They speak to increased dosage of the APP gene acting through heightened levels of Aß42 and/or Aß40 as supporting pathogenesis. These findings further the interest in the potential use of γ-secretase modulators for treating and possibly preventing AD in individuals with DS. ANN NEUROL 2024;96:390-404.

Molecular Imaging of Alzheimer's Disease-Related Sigma-1 Receptor in the Brain via a Novel Ru-Mediated Aromatic 18F-deoxyfluorination Probe.

Sigma-1 receptor (σ1R) is an intracellular protein implicated in a spectrum of neurodegenerative conditions, notably Alzheimer's disease (AD). Positron emission tomography (PET) imaging of brain σ1R could provide a powerful tool for better understanding the underlying pathomechanism of σ1R in AD. In this study, we successfully developed a 18F-labeled σ1R radiotracer [18F]CNY-05 via an innovative ruthenium (Ru)-mediated 18F-deoxyfluorination method. [18F]CNY-05 exhibited preferable brain uptake, high specific binding, and slightly reversible pharmacokinetics within the PET scanning time window. PET imaging of [18F]CNY-05 in nonhuman primates (NHP) indicated brain permeability, metabolic stability, and safety. Moreover, autoradiography and PET studies of [18F]CNY-05 in the AD mouse model found a significantly decreased brain uptake compared to that in wild-type mice. Collectively, we have provided a novel 18F-radiolabeled σ1R PET probe, which enables visualizing brain σ1R in health and neurological diseases.

On the effect heterogeneity of established disease susceptibility loci for Alzheimer's disease across different genetic ancestries.

INTRODUCTION: Genome-wide association studies have identified numerous disease susceptibility loci (DSLs) for Alzheimer's disease (AD). However, only a limited number of studies have investigated the dependence of the genetic effect size of established DSLs on genetic ancestry. METHODS: We utilized the whole genome sequencing data from the Alzheimer's Disease Sequencing Project (ADSP) including 35,569 participants. A total of 25,459 subjects in four distinct populations (African ancestry, non-Hispanic White, admixed Hispanic, and Asian) were analyzed. RESULTS: We found that nine DSLs showed significant heterogeneity across populations. Single nucleotide polymorphism (SNP) rs2075650 in translocase of outer mitochondrial membrane 40 (TOMM40) showed the largest heterogeneity (Cochran's Q = 0.00, I2 = 90.08), followed by other SNPs in apolipoprotein C1 (APOC1) and apolipoprotein E (APOE). Two additional loci, signal-induced proliferation-associated 1 like 2 (SIPA1L2) and solute carrier 24 member 4 (SLC24A4), showed significant heterogeneity across populations. DISCUSSION: We observed substantial heterogeneity for the APOE-harboring 19q13.32 region with TOMM40/APOE/APOC1 genes. The largest risk effect was seen among African Americans, while Asians showed a surprisingly small risk effect.

In Vitro and In Vivo Testing of Microbe Growth on Antimicrobial Nursing Scrubs.

Around 5% to 10% of hospitalized patients develop a hospital-acquired infection (HAI). Scrubs are a potential vector of HAIs. To compare the antimicrobial characteristics of scrubs with and without an antimicrobial fabric coating, as tested in the laboratory (in vitro) and hospital (in vivo) environments. Two protocols were conducted to address the purpose. The in vitro protocol was a laboratory study that involved observing the microbe growth after inoculating coated and uncoated scrub fabric swatches with S. aureus and then processing them in moist and dry environments. The in vivo protocol was a clinical trial that measured microbe growth on coated and uncoated scrubs prior to and following nursing staff completing a 12-hr shift on an acute care unit, as measured by colony forming units (CFUs). For high-humidity environments, the in vitro study indicated that swatches treated with an antimicrobial coating exhibited minimal microbe growth, while untreated swatches exhibited significant microbe growth. For low-humidity environments, coated and uncoated swatches were all found to exhibit minimal microbe growth. In the in vivo study, the CFUs increased on scrubs worn by nurses over a 12-hr shift with no significant difference in CFUs for coated and uncoated scrubs. For bacteria in a warm and moist environment, the antimicrobial coating was found to be important for inhibiting growth. For bacteria in a warm and dry environment, both coated and uncoated fabrics performed similarly as measured at 24 hr, with minimal bacterial growth observed. In a hospital environment, microbe growth was observed, but no significant difference was detected when comparing coated and uncoated scrubs. This may have been due to the short time between exposure and culturing the scrubs for analysis immediately at the end of the shift not allowing for enough time to kill or inhibit growth. Contact time between the bacteria and scrub fabric (coated or uncoated) in the in vivo study more directly correlated with the 0-hr observations for the in vitro study, suggesting that the ineffectiveness of the treated scrubs in the clinical results may be due in part to short residence times before collection.

Sodium oligomannate alters gut microbiota, reduces cerebral amyloidosis and reactive microglia in a sex-specific manner.

It has recently become well-established that there is a connection between Alzheimer's disease pathology and gut microbiome dysbiosis. We have previously demonstrated that antibiotic-mediated gut microbiota perturbations lead to attenuation of Aß deposition, phosphorylated tau accumulation, and disease-associated glial cell phenotypes in a sex-dependent manner. In this regard, we were intrigued by the finding that a marine-derived oligosaccharide, GV-971, was reported to alter gut microbiota and reduce Aß amyloidosis in the 5XFAD mouse model that were treated at a point when Aß burden was near plateau levels. Utilizing comparable methodologies, but with distinct technical and temporal features, we now report on the impact of GV-971 on gut microbiota, Aß amyloidosis and microglial phenotypes in the APPPS1-21 model, studies performed at the University of Chicago, and independently in the 5X FAD model, studies performed at Washington University, St. Louis.Methods To comprehensively characterize the effects of GV-971 on the microbiota-microglia-amyloid axis, we conducted two separate investigations at independent institutions. There was no coordination of the experimental design or execution between the two laboratories. Indeed, the two laboratories were not aware of each other's experiments until the studies were completed. Male and female APPPS1-21 mice were treated daily with 40, 80, or 160 mg/kg of GV-971 from 8, when Aß burden was detectable upto 12 weeks of age when Aß burden was near maximal levels. In parallel, and to corroborate existing published studies and further investigate sex-related differences, male and female 5XFAD mice were treated daily with 100 mg/kg of GV-971 from 7 to 9 months of age when Aß burden was near peak levels. Subsequently, the two laboratories independently assessed amyloid-ß deposition, metagenomic, and neuroinflammatory profiles. Finally, studies were initiated at the University of Chicago to evaluate the metabolites in cecal tissue from vehicle and GV-971-treated 5XFAD mice.Results These studies showed that independent of the procedural differences (dosage, timing and duration of treatment) between the two laboratories, cerebral amyloidosis was reduced primarily in male mice, independent of strain. We also observed sex-specific microbiota differences following GV-971 treatment. Interestingly, GV-971 significantly altered multiple overlapping bacterial species at both institutions. Moreover, we discovered that GV-971 significantly impacted microbiome metabolism, particularly by elevating amino acid production and influencing the tryptophan pathway. The metagenomics and metabolomics changes correspond with notable reductions in peripheral pro-inflammatory cytokine and chemokine profiles. Furthermore, GV-971 treatment dampened astrocyte and microglia activation, significantly decreasing plaque-associated reactive microglia while concurrently increasing homeostatic microglia only in male mice. Bulk RNAseq analysis unveiled sex-specific changes in cerebral cortex transcriptome profiles, but most importantly, the transcriptome changes in the GV-971-treated male group revealed the involvement of microglia and inflammatory responses.Conclusions In conclusion, these studies demonstrate the connection between the gut microbiome, neuroinflammation, and Alzheimer's disease pathology while highlighting the potential therapeutic effect of GV-971. GV-971 targets the microbiota-microglia-amyloid axis, leading to the lowering of plaque pathology and neuroinflammatory signatures in a sex-dependent manner when given at the onset of Aß deposition or when given after Aß deposition is already at higher levels.

Plasma VEGFA and PGF impact longitudinal tau and cognition in preclinical Alzheimer's disease.

Vascular dysfunction is increasingly recognized as an important contributor to the pathogenesis of Alzheimer's disease. Alterations in vascular endothelial growth factor (VEGF) pathways have been implicated as potential mechanisms. However, the specific impact of VEGF proteins in preclinical Alzheimer's disease and their relationships with other Alzheimer's disease and vascular pathologies during this critical early period remain to be elucidated. We included 317 older adults from the Harvard Aging Brain Study, a cohort of individuals who were cognitively unimpaired at baseline and followed longitudinally for up to 12 years. Baseline VEGF family protein levels (VEGFA, VEGFC, VEGFD, PGF and FLT1) were measured in fasting plasma using high-sensitivity immunoassays. Using linear mixed effects models, we examined the interactive effects of baseline plasma VEGF proteins and amyloid PET burden (Pittsburgh Compound-B) on longitudinal cognition (Preclinical Alzheimer Cognitive Composite-5). We further investigated if effects on cognition were mediated by early neocortical tau accumulation (flortaucipir PET burden in the inferior temporal cortex) or hippocampal atrophy. Lastly, we examined the impact of adjusting for baseline cardiovascular risk score or white matter hyperintensity volume. Baseline plasma VEGFA and PGF each showed a significant interaction with amyloid burden on prospective cognitive decline. Specifically, low VEGFA and high PGF were associated with greater cognitive decline in individuals with elevated amyloid, i.e. those on the Alzheimer's disease continuum. Concordantly, low VEGFA and high PGF were associated with accelerated longitudinal tau accumulation in those with elevated amyloid. Moderated mediation analyses confirmed that accelerated tau accumulation fully mediated the effects of low VEGFA and partially mediated (31%) the effects of high PGF on faster amyloid-related cognitive decline. The effects of VEGFA and PGF on tau and cognition remained significant after adjusting for cardiovascular risk score or white matter hyperintensity volume. There were concordant but non-significant associations with longitudinal hippocampal atrophy. Together, our findings implicate low VEGFA and high PGF in accelerating early neocortical tau pathology and cognitive decline in preclinical Alzheimer's disease. Additionally, our results underscore the potential of these minimally-invasive plasma biomarkers to inform the risk of Alzheimer's disease progression in the preclinical population. Importantly, VEGFA and PGF appear to capture distinct effects from vascular risks and cerebrovascular injury. This highlights their potential as new therapeutic targets, in combination with anti-amyloid and traditional vascular risk reduction therapies, to slow the trajectory of preclinical Alzheimer's disease and delay or prevent the onset of cognitive decline.

Correction: Palmitoylated APP Forms Dimers, Cleaved by BACE1.

[This corrects the article DOI: 10.1371/journal.pone.0166400.].

Early modulation of the gut microbiome by female sex hormones alters amyloid pathology and microglial function.

It is well-established that women are disproportionately affected by Alzheimer's disease. The mechanisms underlying this sex-specific disparity are not fully understood, but several factors that are often associated-including interactions of sex hormones, genetic factors, and the gut microbiome-likely contribute to the disease's etiology. Here, we have examined the role of sex hormones and the gut microbiome in mediating Aß amyloidosis and neuroinflammation in APPPS1-21 mice. We report that postnatal gut microbiome perturbation in female APPPS1-21 mice leads to an elevation in levels of circulating estradiol. Early stage ovariectomy (OVX) leads to a reduction of plasma estradiol that is correlated with a significant alteration of gut microbiome composition and reduction in Aß pathology. On the other hand, supplementation of OVX-treated animals with estradiol restores Aß burden and influences gut microbiome composition. The reduction of Aß pathology with OVX is paralleled by diminished levels of plaque-associated microglia that acquire a neurodegenerative phenotype (MGnD-type) while estradiol supplementation of OVX-treated animals leads to a restoration of activated microglia around plaques. In summary, our investigation elucidates the complex interplay between sex-specific hormonal modulations, gut microbiome dynamics, metabolic perturbations, and microglial functionality in the pathogenesis of Alzheimer's disease.

Structure-Based Discovery of A Small Molecule Inhibitor of Histone Deacetylase 6 (HDAC6) that Significantly Reduces Alzheimer's Disease Neuropathology.

Histone deacetylase 6 (HDAC6) is one of the key histone deacetylases (HDACs) that regulates various cellular functions including clearance of misfolded protein and immunological responses. Considerable evidence suggests that HDAC6 is closely related to amyloid and tau pathology, the two primary hallmarks of Alzheimer's disease (AD). It is still unclear whether HDAC6 expression changes with amyloid deposition in AD during disease progression or HDAC6 may be regulating amyloid phagocytosis or neuroinflammation or other neuropathological changes in AD. In this work, the pathological accumulation of HDAC6 in AD brains over age as well as the relationship of its regulatory activity - with amyloid pathogenesis and pathophysiological alterations is aimed to be enlightened using the newly developed HDAC6 inhibitor (HDAC6i) PB118 in microglia BV2 cell and 3D-AD human neural culture model. Results suggest that the structure-based rational design led to biologically compelling HDAC6i PB118 with multiple mechanisms that clear Aß deposits by upregulating phagocytosis, improve tubulin/microtubule network by enhancing acetyl α-tubulin levels, regulate different cytokines and chemokines responsible for inflammation, and significantly reduce phospho-tau (p-tau) levels associated with AD. These findings indicate that HDAC6 plays key roles in the pathophysiology of AD and potentially serves as a suitable pharmacological target through chemical biology-based drug discovery in AD.

The predictive validity of a Brain Care Score for dementia and stroke: data from the UK Biobank cohort.

Introduction: The 21-point Brain Care Score (BCS) was developed through a modified Delphi process in partnership with practitioners and patients to promote behavior changes and lifestyle choices in order to sustainably reduce the risk of dementia and stroke. We aimed to assess the associations of the BCS with risk of incident dementia and stroke. Methods: The BCS was derived from the United Kingdom Biobank (UKB) baseline evaluation for participants aged 40-69 years, recruited between 2006-2010. Associations of BCS and risk of subsequent incident dementia and stroke were estimated using Cox proportional hazard regressions, adjusted for sex assigned at birth and stratified by age groups at baseline. Results: The BCS (median: 12; IQR:11-14) was derived for 398,990 UKB participants (mean age: 57; females: 54%). There were 5,354 incident cases of dementia and 7,259 incident cases of stroke recorded during a median follow-up of 12.5 years. A five-point higher BCS at baseline was associated with a 59% (95%CI: 40-72%) lower risk of dementia among participants aged <50. Among those aged 50-59, the figure was 32% (95%CI: 20-42%) and 8% (95%CI: 2-14%) for those aged >59 years. A five-point higher BCS was associated with a 48% (95%CI: 39-56%) lower risk of stroke among participants aged <50, 52% (95%CI, 47-56%) among those aged 50-59, and 33% (95%CI, 29-37%) among those aged >59. Discussion: The BCS has clinically relevant and statistically significant associations with risk of dementia and stroke in approximately 0.4 million UK people. Future research includes investigating the feasibility, adaptability and implementation of the BCS for patients and providers worldwide.

Development and Pharmacochemical Characterization Discover a Novel Brain-Permeable HDAC11-Selective Inhibitor with Therapeutic Potential by Regulating Neuroinflammation in Mice.

Recent studies have shown that the epigenetic protein histone deacetylase 11 (HDAC11) is highly expressed in the brain and critically modulates neuroimmune functions, making it a potential therapeutic target for neurological disorders. Herein, we report the development of PB94, which is a novel HDAC11 inhibitor. PB94 exhibited potency and selectivity against HDAC11 with IC50 = 108 nM and >40-fold selectivity over other HDAC isoforms. Pharmacokinetic/pharmacodynamic evaluation indicated that PB94 possesses promising drug-like properties. Additionally, PB94 was radiolabeled with carbon-11 as [11C]PB94 for positron emission tomography (PET), which revealed significant brain uptake and metabolic properties suitable for drug development in live animals. Furthermore, we demonstrated that neuropathic pain was associated with brain upregulation of HDAC11 and that pharmacological inhibition of HDAC11 by PB94 ameliorated neuropathic pain in a mouse model. Collectively, our findings support further development of PB94 as a selective HDAC11 inhibitor for neurological indications, including pain.

PS1/gamma-secretase acts as rogue chaperone of glutamate transporter EAAT2/GLT-1 in Alzheimer's disease.

The recently discovered interaction between presenilin 1 (PS1), a catalytic subunit of γ-secretase responsible for the generation of amyloid-ß(Aß) peptides, and GLT-1, the major glutamate transporter in the brain (EAAT2 in the human) may provide a mechanistic link between two important pathological aspects of Alzheimer's disease (AD): abnormal Aßoccurrence and neuronal network hyperactivity. In the current study, we employed a FRET-based approach, fluorescence lifetime imaging microscopy (FLIM), to characterize the PS1/GLT-1 interaction in its native environment in the brain tissue of sporadic AD (sAD) patients. There was significantly less interaction between PS1 and GLT-1 in sAD brains, compared to tissue from patients with frontotemporal lobar degeneration (FTLD), or non-demented age-matched controls. Since PS1 has been shown to adopt pathogenic "closed" conformation in sAD but not in FTLD, we assessed the impact of changes in PS1 conformation on the interaction. Familial AD (fAD) PS1 mutations which induce a "closed" PS1 conformation similar to that in sAD brain and gamma-secretase modulators (GSMs) which induce a "relaxed" conformation, reduced and increased the interaction, respectively. This indicates that PS1 conformation seems to have a direct effect on the interaction with GLT-1. Furthermore, using biotinylation/streptavidin pull-down, western blotting, and cycloheximide chase assays, we determined that the presence of PS1 increased GLT-1 cell surface expression and GLT-1 homomultimer formation, but did not impact GLT-1 protein stability. Together, the current findings suggest that the newly described PS1/GLT-1 interaction endows PS1 with chaperone activity, modulating GLT-1 transport to the cell surface and stabilizing the dimeric-trimeric states of the protein. The diminished PS1/GLT-1 interaction suggests that these functions of the interaction may not work properly in AD.

Accelerating the in vitro emulation of Alzheimer's disease-associated phenotypes using a novel 3D blood-brain barrier neurosphere co-culture model.

High failure rates in clinical trials for neurodegenerative disorders such as Alzheimer's disease have been linked to an insufficient predictive validity of current animal-based disease models. This has created an increasing demand for alternative, human-based models capable of emulating key pathological phenotypes in vitro. Here, a three-dimensional Alzheimer's disease model was developed using a compartmentalized microfluidic device that combines a self-assembled microvascular network of the human blood-brain barrier with neurospheres derived from Alzheimer's disease-specific neural progenitor cells. To shorten microfluidic co-culture times, neurospheres were pre-differentiated for 21 days to express Alzheimer's disease-specific pathological phenotypes prior to the introduction into the microfluidic device. In agreement with post-mortem studies and Alzheimer's disease in vivo models, after 7 days of co-culture with pre-differentiated Alzheimer's disease-specific neurospheres, the three-dimensional blood-brain barrier network exhibited significant changes in barrier permeability and morphology. Furthermore, vascular networks in co-culture with Alzheimer's disease-specific microtissues displayed localized ß-amyloid deposition. Thus, by interconnecting a microvascular network of the blood-brain barrier with pre-differentiated neurospheres the presented model holds immense potential for replicating key neurovascular phenotypes of neurodegenerative disorders in vitro.

Multivariate GWAS of Alzheimer's disease CSF biomarker profiles implies GRIN2D in synaptic functioning.

BACKGROUND: Genome-wide association studies (GWAS) of Alzheimer's disease (AD) have identified several risk loci, but many remain unknown. Cerebrospinal fluid (CSF) biomarkers may aid in gene discovery and we previously demonstrated that six CSF biomarkers (ß-amyloid, total/phosphorylated tau, NfL, YKL-40, and neurogranin) cluster into five principal components (PC), each representing statistically independent biological processes. Here, we aimed to (1) identify common genetic variants associated with these CSF profiles, (2) assess the role of associated variants in AD pathophysiology, and (3) explore potential sex differences. METHODS: We performed GWAS for each of the five biomarker PCs in two multi-center studies (EMIF-AD and ADNI). In total, 973 participants (n = 205 controls, n = 546 mild cognitive impairment, n = 222 AD) were analyzed for 7,433,949 common SNPs and 19,511 protein-coding genes. Structural equation models tested whether biomarker PCs mediate genetic risk effects on AD, and stratified and interaction models probed for sex-specific effects. RESULTS: Five loci showed genome-wide significant association with CSF profiles, two were novel (rs145791381 [inflammation] and GRIN2D [synaptic functioning]) and three were previously described (APOE, TMEM106B, and CHI3L1). Follow-up analyses of the two novel signals in independent datasets only supported the GRIN2D locus, which contains several functionally interesting candidate genes. Mediation tests indicated that variants in APOE are associated with AD status via processes related to amyloid and tau pathology, while markers in TMEM106B and CHI3L1 are associated with AD only via neuronal injury/inflammation. Additionally, seven loci showed sex-specific associations with AD biomarkers. CONCLUSIONS: These results suggest that pathway and sex-specific analyses can improve our understanding of AD genetics and may contribute to precision medicine.

SARS-CoV-2 reservoir in post-acute sequelae of COVID-19 (PASC).

Millions of people are suffering from Long COVID or post-acute sequelae of COVID-19 (PASC). Several biological factors have emerged as potential drivers of PASC pathology. Some individuals with PASC may not fully clear the coronavirus SARS-CoV-2 after acute infection. Instead, replicating virus and/or viral RNA-potentially capable of being translated to produce viral proteins-persist in tissue as a 'reservoir'. This reservoir could modulate host immune responses or release viral proteins into the circulation. Here we review studies that have identified SARS-CoV-2 RNA/protein or immune responses indicative of a SARS-CoV-2 reservoir in PASC samples. Mechanisms by which a SARS-CoV-2 reservoir may contribute to PASC pathology, including coagulation, microbiome and neuroimmune abnormalities, are delineated. We identify research priorities to guide the further study of a SARS-CoV-2 reservoir in PASC, with the goal that clinical trials of antivirals or other therapeutics with potential to clear a SARS-CoV-2 reservoir are accelerated.