Alzheimer's Research & Therapy

INTRODUCTIONCerebrovascular reactivity (CVR) impairment is a key feature of Alzheimers disease (AD), but its mechanistic basis remains unclear. This study examined whether vascular smooth muscle cell (VSMC) loss, rather than amyloidosis or neuroinflammation, underlies CVR deficits. METHODSNon-contrast MRI, including phase-contrast and pseudo-continuous arterial spin labeling, was performed in mouse models of amyloidosis (5xFAD), VSMC degeneration (CADASIL), and lipopolysaccharide-induced neuroinflammation. Characterization of vascular, amyloid-{beta}, and inflammatory markers were performed for pathological assessment. RESULTSCVR impairment emerged only when VSMC loss was present in CADASIL mice and at older ages in 5xFAD mice (9-12 months). Amyloid-{beta} deposition occurred earlier than VSMC loss or CVR decline. Neuroinflammation primarily altered baseline cerebral blood flow without affecting CVR or VSMC integrity. DISCUSSIONThese findings identify VSMC degeneration as an important driver of CVR impairment independent of cerebral amyloid angiopathy or inflammation, highlighting vascular integrity as a potential therapeutic target in AD. HighlightsO_LICerebrovascular reactivity (CVR) impairment occurred in 5xFAD mice only when vascular smooth muscle cell (VSMC) loss was present C_LIO_LI5xFAD mice exhibited prominent parenchymal but minimal vascular amyloid-{beta} deposition C_LIO_LIVSMC developmental deficiency resulted in CVR impairment in a small-vessel disease (SVD) model C_LIO_LINeuroinflammation primarily altered baseline cerebral blood flow (CBF) without affecting CVR C_LI

Pyroglutamate-3 amyloid-{beta} (pGlu3 A{beta}) is an N-terminally modified, toxic form of amyloid-{beta} that is present in cerebral amyloid plaques and vascular deposits. Using the Fc-competent murine anti-pGlu3 A{beta} monoclonal antibody (mAb), 07/2a, we present here a nonpharmacological approach using focused ultrasound (FUS) with intravenous (i.v.) injection of microbubbles (MB) to facilitate i.v. delivery of the 07/2a mAb across the blood brain barrier (BBB) in order to improve A{beta} removal and restore memory in aged APP/PS1 mice, an Alzheimers disease (AD)-like model of amyloidogenesis. Compared to sham-treated controls, aged APP/PS1 mice treated with 07/2a immediately prior to FUS-mediated BBB disruption (mAb + FUS-BBBD combination treatment) showed significantly better spatial learning and memory in the Water T Maze. FUS-BBBD treatment alone improved contextual fear learning and memory in aged WT and APP/PS1 mice, respectively. APP/PS1 mice given the combination treatment had reduced A{beta}42 and pGlu3 A{beta} hippocampal plaque burden compared to PBS-treated APP/PS1 mice. Hippocampal synaptic puncta density and synaptosomal synaptic protein levels were also higher in APP/PS1 mice treated with 07/2a just prior to BBB disruption. Increased Iba-1+ microglia were observed in the hippocampi of AD mice treated with 07/2a with and without FUS-BBBD, and APP/PS1 mice that received hippocampal BBB disruption and 07/2a showed increased Ly6G+ monocytes in hippocampal CA3. FUS-induced BBB disruption did not increase the incidence of microhemorrhage in mice with or without 07/2a mAb treatment. Our findings suggest that FUS is useful tool that may enhance delivery of an anti-pGlu3 A{beta} mAb for immunotherapy. FUS-mediated BBB disruption in combination with the 07/2a mAb also appears to facilitate monocyte infiltration in this AD model. Overall, these effects resulted in greater sparing of synapses and improved cognitive function without causing overt damage, suggesting the possibility of FUS as a noninvasive method to increase the therapeutic efficacy in AD patients.

AD pathology is accompanied by increased senescence and reduced levels of autophagy in the brain. We investigated whether pharmacologically inducing autophagy could alter the senescent phenotype and help ameliorate AD pathology. We discovered that Bisdemethoxycurcumin (BDMC), a natural compound found in Curcuma longa, stimulates autophagy in primary astrocytes. We found that autophagy and senescence exhibit an inverse relationship in aging astrocytes, with increased expression of senescent proteins and downregulation of autophagic proteins. However, treatment of aged astrocytes with BDMC reversed the senescent phenotype by ameliorating the impaired autophagy. Interestingly, the senescent phenotype persisted when autophagy was downregulated by knockdown of AMPK. Additionally, BDMC-induced autophagy aided in the removal of amyloid beta that was administered externally to the astrocytes. Further, to validate these results in a mouse model of AD, we confirmed that BDMC can significantly penetrate the blood-brain barrier (BBB) in mice. Therefore, we administered 50 and 100 mg/kg b.w. of BDMC to transgenic 3xTg-AD mice for two months. In their hippocampus, the Control 3xTg-AD animals showed more senescent cells and lower autophagy levels. In contrast, autophagic proteins were significantly upregulated while senescence indicators, such as senescence-associated secretory phenotype (SASP) proteins, were sharply downregulated in the brain of treated animals. Additionally, we discovered that the treated mices hippocampus had a significantly lower amyloid beta load. These molecular changes in the brain were ultimately reflected in the improved working memory and neuromuscular coordination behavior of mice treated with BDMC. This study warrants further evaluation of BDMC for the management of AD. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=139 SRC="FIGDIR/small/654834v1_ufig1.gif" ALT="Figure 1"> View larger version (53K): org.highwire.dtl.DTLVardef@1176bbforg.highwire.dtl.DTLVardef@a2e2cdorg.highwire.dtl.DTLVardef@1d824f5org.highwire.dtl.DTLVardef@1628a30_HPS_FORMAT_FIGEXP M_FIG This illustration was created by using biorender.com C_FIG

INTRODUCTIONReduced somatostatin (SST) and SST-expressing GABAergic neurons are well-replicated findings in Alzheimers disease (AD) and are associated with cognitive deficits. SST cells inhibit pyramidal cell dendrites through 5-GABA-A receptors (5-GABAA-R). 5-GABAAR positive allosteric modulation (5-PAM) has procognitive and neurotrophic effects in stress and aging models. METHODSWe tested whether 5-PAM (GL-II-73) could reverse cognitive deficits and neuronal spine loss in early and late stages of {beta}-amyloid deposition in the 5xFAD model (N=48/study; 50% female). RESULTSAcute or chronic administration of GL-II-73 reversed spatial working memory in 5xFAD mice at 2 and 5 months of age. Chronic GL-II-73 treatment reversed 5xFAD-induced loss of spine density, spine count and dendritic length at both time points, despite {beta}-amyloid accumulation. DISCUSSIONThese results demonstrate procognitive and neurotrophic effects of GL-II-73 in early and late stages of Alzheimer-related {beta}-amyloid deposition. This suggests 5-PAM as a novel {beta}-amyloid-independent symptomatic therapeutic approach.

Alzheimers disease (AD) is the most common cause of dementia and identifying early markers of this disease is important for prevention and treatment strategies. Amyloid - {beta} protein deposition is one of the earliest detectable pathological changes in AD. But in-vivo detection of amyloid - {beta} using positron emission tomography (PET) is hampered by high cost and limited geographical accessibility. These factors can become limiting when PET is used to screen large numbers of subjects into prevention trials when only a minority are expected to be amyloid- {beta} - positive. Structural MRI is advantageous; as it is relatively inexpensive and more accessible. Thus it could be widely used in large studies, even when frequent or repetitive imaging is necessary. We used a machine learning, pattern recognition, approach using intensity-based features from individual and combination of MR modalities (T1 weighted, T2 weighted, T2 fluid attenuated inversion recovery [FLAIR], susceptibility weighted imaging) to predict voxel-level amyloid- {beta} in the brain. The MR- amyloid {beta} relation was learned within each subject and generalized across subjects using subject-specific features (demographic, clinical, and summary MR features). When compared to other modalities, combination of T1-weighted, T2-weighted FLAIR, and SWI performed best in predicting the amyloid- {beta} status as positive or negative. T2- weighted performed the best in predicting change in amyloid- {beta} over two timepoints. Overall, our results show feasibility of amyloid- {beta} prediction by MRI.

BackgroundFluoroethylnormemantine (FENM), a new Memantine (MEM) derivative, prevented amyloid-{beta}[25-35] peptide (A{beta}25-35)-induced neurotoxicity in mice, a pharmacological model of Alzheimers disease (AD) with high predictive value for drug discovery. Here, as drug infusion is likely to better reflect drug bioavailability due to the interspecies pharmacokinetics variation, we analyzed the efficacy of FENM after chronic subcutaneous (SC) infusion, in comparison with IP injections in two AD mouse models, A{beta}25-35 -injected mice and the transgenic APP /PSEN1{partial}E9 (APP/PS1) line. MethodsIn A{beta}25-35-treated mice, FENM was infused at 0.03-0.3 mg/kg/day during one week after A{beta}25-35 injection. For comparison, FENM and MEM were administered IP daily at 0.03-0.3 mg/kg. In 10-month-old APP/PS1 mice, FENM was administered during four weeks by daily IP injections at 0.3 mg/kg or chronic SC infusion at 0.1 mg/kg/day. Memory deficits, spatial working memory and recognition memory, were analysed. Markers of neuroinflammation, apoptosis, oxidative stress, and amyloid burden in APP/PS1 mice, were quantified. Markers of synaptic plasticity such as PSD-95 and GluN2A/B/D subunits expression in hippocampus homogenates or synaptosomes were quantified in A{beta}25-35-treated mice and synaptic long-term potentiation (LTP) in hippocampal slices was analysed in APP/PS1 mice. ResultsDeficits in spontaneous alternation and object recognition in A{beta}25-35 mice were prevented by infused FENM at all doses tested. Similar effects were observed with the daily FENM or MEM treatments. Animals infused with 0.1 mg/kg/day FENM showed prevention of A{beta}25-35-induced neuroinflammation, oxidative stress and apoptosis. FENM infusion restored A{beta}25-35-induced alterations in synaptosomal PSD-95, GluN2A and P-GluN2B levels. GluN2D levels were unchanged whatever the treatment. In APP/PS1 mice, FENM infused or administered IP alleviated spontaneous alternation deficits, neuroinflammation, increases in A{beta}1-40/A{beta}1-42 and hippocampal LTP alteration. ConclusionThese data confirmed the neuroprotective potential of FENM in the pharmacological A{beta}25-35 and transgenic APP/PS1 mouse models of AD, with a superiority to MEM, and showed that the drug can be efficiently infused chronically.

BackgroundAdvance care planning (ACP) and advance directives (AD) are tools for supporting person-centered decision-making. In dementia care, the progression of cognitive decline, complex family dynamics and variability in healthcare systems pose unique challenges to effective ACP/AD implementation for people with dementia (PWD). MethodsWe conducted a scoping review of the literature related to ACP/AD in dementia care between 2014-2024. Studies were screened and thematically analyzed to identify current approaches, gaps and recommendations for dementia-specific ACP/AD. We identified key stakeholders involved in decision-making and highlighted procedural components for ACP/AD according to stakeholder groups. ResultsForty studies were included. Key stakeholders included healthcare professionals (HCPs); family members and caregivers; PWD; dyads (PWD and their caregivers); the broader public; policymakers; and researchers. Prominent findings included: the role and training of HCPs; educational and decision-support needs; early and ongoing engagement of PWD; development and evaluation of dementia-specific tools; ethical and procedural challenges in end-of-life decision-making; and the importance of outreach and cultural sensitivity. Promising interventions include structured communication models, psychoeducational programs and tools, although few have been fully adapted for dementia. ConclusionDementia-specific ACP/AD require a relational, flexible and ethically grounded approach that evolves with the individuals condition. While ACP/AD should reflect the autonomous preferences of the PWD, during late-stage dementia, shared decision-making becomes central to providing care that aligns with the persons goals and preferences. Future research should focus on inclusive tools and training; timing and process facilitation; and public health strategies to improve access and equity.

Alzheimers disease (AD) is a neurodegenerative disorder characterized by cognitive decline and the accumulation of beta-amyloid plaques and neurofibrillary tangles. Microglia, the resident immune cells in the brain, play a crucial role in AD pathology, particularly in relation to amyloid plaques. However, the exact role of plaque-associated microglia and their morphological changes in AD progression remains under debate. In this study, we aimed to establish an automated image segmentation and analysis pipeline optimized for the detection of human microglia, and we assessed its utility by systematically investigating topological relationships between microglia morphology and amyloid plaques. We accessed post-mortem brain tissue samples from persons with AD and utilized immunofluorescence staining to label microglia (IBA1) and amyloid plaques (A{beta}1-42). The acquired images were processed using CellProfiler, an open-source image analysis software, to automatically segment microglia and measure their morphological features. Specifically, since activated (stage III) microglia have a condensed morphology with retracted processes, we prioritized a morphological parameter called "compactness" in our analyses to capture shape changes in microglial found in proximity to amyloid plaques. Our results revealed that microglia unassociated with plaques (Mip-) were more abundant than microglia associated with plaques (Mip+) in the Dorsolateral Prefrontal Cortex (DLPFC) of both men and women with AD. Furthermore, we observed that Mip+ exhibited a significantly more ramified shape and had a higher expression of the IBA1 microglial marker gene compared to Mip. There were no significant differences in microglia morphology between men and women. Our study highlights the utility of automated image analysis in characterizing detailed microglia morphology at the single-cell level and its relationship with AD pathology.

IntroductionCerebral amyloid angiopathy (CAA) is characterized by the aggregation of amyloid-{beta} peptides in cerebral blood vessels, leading to a loss of vascular integrity and contributing to the progression of Alzheimers disease (AD). In our previous study, we showed that short-term treatment with the antiplatelet drug clopidogrel, a P2Y12 inhibitor that irreversibly blocks ADP signaling, reduced the incidence of CAA in the APP23 mouse model of Alzheimers disease providing strong evidence for platelets to contribute to AD pathology. The objective of the present study was to ascertain whether long-term treatment with clopidogrel and the earlier initiation of treatment prior to the formation of A{beta} deposits prevents pathological changes associated with Alzheimers disease. MethodsAPP23 mice were treated with clopidogrel for 15 month and analyzed for AD pathology. ResultsWe detected increased permeability of the blood brain barrier in different brains regions of APP23 mice. Moreover, platelets migrated into the brain parenchyma and accumulated around amyloid plaques in the brain of APP23 mice. Although we detected platelets in close proximity to microglia and neurons in the cortex and hippocampus of APP23 mice, we did not observe any differences in neurodegeneration or gliosis in Clopidogrel treated APP23 mice. Furthermore, pathological analysis showed a significant reduction in CAA and in soluble A{beta}42 levels in the brain of Clopidogrel versus placebo treated APP23 mice but no differences in plaque load in the brain parenchyma. ConclusionThus, antiplatelet therapy may alleviate amyloid pathology in cerebral vessels leading to improved blood perfusion in AD patients.

BackgroundFocused ultrasound (FUS) in combination with microbubbles has recently shown great promise in facilitating blood-brain barrier (BBB) opening for drug delivery and immunotherapy in Alzheimers disease (AD). However, it is currently limited to systems integrated within the MRI suites or requiring post-surgical implants, thus restricting its widespread clinical adoption. In this pilot study, we investigate the clinical safety and feasibility of a portable, non-invasive neuronavigation-guided FUS (NgFUS) system with integrated real-time 2-D microbubble cavitation mapping. MethodsA phase 1 clinical study with mild to moderate AD patients (N=6) underwent a single session of microbubble-mediated NgFUS to induce transient BBB opening (BBBO). Microbubble activity under FUS was monitored with real-time 2-D cavitation maps and dosing to ensure the efficacy and safety of the NgFUS treatment. Post-operative MRI was used for BBB opening and closure confirmation as well as safety assessment. Changes in AD biomarker levels in both blood serum and extracellular vesicles (EVs) were evaluated, while changes in amyloid-beta (A{beta}) load in the brain were assessed through 18F-Florbetapir PET. ResultsBBBO was achieved in 5 out of 6 subjects with an average volume of 983{+/-}626 mm3 following FUS at the right frontal lobe both in white and gray matter regions. The outpatient treatment was completed within 34.8{+/-}10.7 min. Cavitation dose significantly correlated with the BBBO volume (R2>0.9, N=4), demonstrating the portable NgFUS systems capability of predicting opening volumes. The cavitation maps co-localized closely with the BBBO location, representing the first report of real-time transcranial 2-D cavitation mapping in the human brain. Larger opening volumes correlated with increased levels of AD biomarkers, including A{beta}42 (R2=0.74), Tau (R2=0.95), and P-Tau181 (R2=0.86), assayed in serum-derived EVs sampled 3 days after FUS (N=5). From PET scans, subjects showed a lower A{beta} load increase in the treated frontal lobe region compared to the contralateral region. Reduction in asymmetry standardized uptake value ratios (SUVR) correlated with the cavitation dose (R2>0.9, N=3). Clinical changes in the mini-mental state examination over 6 months were within the expected range of cognitive decline with no additional changes observed as a result of FUS. ConclusionWe showed the safety and feasibility of this cost-effective and time-efficient portable NgFUS treatment for BBBO in AD patients with the first demonstration of real-time 2-D cavitation mapping. The cavitation dose correlated with BBBO volume, a slowed increase in pathology, and serum detection of AD proteins. Our study highlights the potential for accessible FUS treatment in AD, with or without drug delivery.

Alzheimers disease (AD) is characterized neuropathologically by amyloid-{beta} (A{beta}) plaques and neurofibrillary tangles. Vascular pathology caused by chronic cerebral hypoperfusion (HP) is hypothesised to exacerbate AD pathology and has emerged as an increasing cause of age-related cognitive impairment. In this study we examined the effects of gradual cerebral HP on cognitive dysfunction, A{beta} pathology, microgliosis, and cortical network dynamics in C57BL/6J mice and a single App knock-in mouse model of AD (AppNL-G-F). We performed unilateral common carotid artery gradual occlusion (UCAgO) in two-month-old mice using an ameroid constrictor. At 4 months of age, animals were tested in a behavioral battery consisting of tests of spatial learning and memory (Morris water task), recognition memory (novel object recognition task), and motor coordination (balance beam). Following behavioural testing, in vivo mesoscale wide-field voltage imaging was done to assess cortical functional connectivity and sensory-evoked cortical activity, and brains were harvested for pathology characterization using immunohistochemistry. We found that UCAgO reduced cerebral blood flow (CBF) in the occluded hemisphere (OH), however, subtle behavioural deficits were observed due to HP. A dissociative effect of HP was observed in resting-state functional connectivity analysis, where HP led to hyper-connectivity in C57 mice and hypo-connectivity in App mice. Interestingly, sensory stimulation of limbs contralateral to OH revealed hyper-cortical activations in the non-occluded hemisphere of C57 HP mice, however, hypo-cortical activations were observed in App HP mice. Furthermore, we found that the UCAgO increased cortical and hippocampal microgliosis in both hemispheres of C57 and App mice, a bilateral increase in A{beta} deposition was only observed in App mice. These results suggest that gradual cerebral HP leads to cortical network alterations in AD, which is partly mediated via activation of microglia.

Predicting the likelihood of developing Alzheimers disease (AD) dementia in at-risk individuals is important for the design of and optimal recruitment for clinical trials of disease-modifying therapies. Machine learning (ML) has been shown to excel in this task; however, there remains a lack of models developed specifically for the preclinical AD population, who display early signs of abnormal brain amyloidosis but remain cognitively unimpaired. Here, we trained and evaluated ML classifiers to predict whether individuals with preclinical AD will progress to mild cognitive impairment or dementia within multiple fixed time windows, ranging from one to five years. Models were trained on regional imaging features extracted from amyloid positron emission tomography and magnetic resonance imaging pooled across seven independent sites and from two amyloid radiotracers ([18F]-florbetapir and [11C]-Pittsburgh-compound-B). Out-of-sample generalizability was evaluated via a leave-one-site-out and leave-one-tracer-out cross-validation. Classifiers achieved an out-of-sample receiver operating characteristic area-under-the-curve of 0.66 or greater when applied to all except one hold-out sites and 0.72 or greater when applied to each hold-out radiotracer. Additionally, when applying our models in a retroactive cohort enrichment analysis on A4 clinical trial data, we observed increased statistical power of detecting differences in amyloid accumulation between placebo and treatment arms after enrichment by ML stratifications. As emerging investigations of new disease-modifying therapies for AD increasingly focus on asymptomatic, preclinical populations, our findings underscore the potential applicability of ML-based patient stratification for recruiting more homogeneous cohorts and improving statistical power for detecting treatment effects for future clinical trials. HighlightsO_LIMachine learning can predict future cognitive impairment in preclinical Alzheimers C_LIO_LIModels achieved high out-of-sample ROC-AUC on external sites and PET tracers C_LIO_LIModels were able to distinguish cognitively stable from decliners in the A4 cohort C_LIO_LIML cohort enrichment enhanced secondary treatment effect detection in the A4 cohort C_LI

Chronic neuroinflammation in Alzheimers disease (AD) activates astrocytes--key regulators of both brain immunity and neurovascular coupling. The primed immune environment in AD brain also renders it highly susceptible to secondary systemic inflammatory challenges. Inflammatory activation drives phenotypic shifts in astrocytes that may compromise their ability to regulate cerebral blood flow. The capacity for inflammation-activated astrocytes to retain this regulatory function, however, remains unknown. To investigate astrocyte regulation of cerebral blood flow in AD brain and under systemic inflammation, we investigated astrocytic Ca2+ dynamics and functional hyperemia at rest and during brief and prolonged sensory stimulation in 12-month-old female APP/PS1dE9 mice. We further examined how a secondary systemic inflammatory challenge induced by low-dose, repeated injection of LPS modulates astrocytic signaling and neurovascular function. AD mice exhibited elevated spontaneous but diminished stimulation-evoked astrocytic Ca2+ activity, accompanied by impaired sustained functional hyperemia, particularly within the capillary network. LPS-induced systemic inflammation further suppressed both spontaneous and evoked astrocytic Ca2+ responses and attenuated functional hyperemia. Together, these findings reveal that inflammation disrupts astrocyte-dependent regulation of sustained neurovascular responses in the AD brain. HIGHLIGHTSO_LIAstrocytes in AD mice exhibit increased spontaneous Ca2+ signaling but cannot sustain stimulus-evoked Ca2+ release. C_LIO_LIReduced astrocyte Ca2+ release during 30s functional brain activation correlates with impaired neurovascular coupling in both penetrating arterioles and capillaries of AD mice C_LIO_LIA secondary, 14-day systemic inflammatory challenge further suppressed functional hyperemia of 30 s stimulus-evoked astrocytic Ca2+ release in AD mice. C_LIO_LIA secondary inflammatory insult lasting 14 days reduced amyloid deposition in the AD brain. C_LI

Studying brain gene expression in Alzheimers Disease (AD) presents significant challenges as postmortem brain tissue data is difficult to access, cannot be used to guide donor treatment, may be affected by confounding environmental factors before and after death and is difficult to link to early AD states or disease progression. To circumvent these limitations, several studies have tested blood transcriptome biomarkers for AD. However, gene-expression levels in the blood have limited correlation with those in the brain. Therefore, to test the potential of monitoring Alzheimers progression with peripheral data, we used a transcriptome-imputation method, to identify brain-region-specific AD-associated gene-expression differences in multiple cohorts with available blood-based transcriptome data. This approach provides a high-resolution image of the AD-associated molecular differences in the brains of affected individuals actively living with disease. We analyzed eight AD studies (777 AD cases, 779 cognitively unimpaired controls) in which we imputed brain-regional gene expression in 10 brain areas, using Brain Gene Expression and Network Imputation Engine (BrainGENIE). Hundreds of differentially expressed genes (DEGs) associated with AD were identified in nine brain regions, with anterior cingulate cortex and amygdala showing the most differential expression. AD-associated genes were enriched in pathways related to proteostasis, mitochondrial dysfunction, and immune activation, among others. We observed significant congruence between imputed AD-associated changes and those directly measured in the dorsolateral prefrontal cortex and cerebellum. These transcriptomic changes can be leveraged in future in vitro studies focused on pathogenesis, or as the targets of novel therapeutic developments. In conclusion, we demonstrated the scope and utility of brain expression imputation from the peripheral transcriptome, laying the groundwork for biomarker discovery and prospective studies on the aging brain and AD.

BackgroundP-glycoprotein (P-gp/ABCB1) is a key efflux transporter that maintains barrier integrity by clearing xenobiotics and toxic metabolites. At the feto-maternal interface, trophoblast-derived extracellular vesicles (CTC-EVs) naturally and transiently transfer functional P-gp to maternal decidual cells, restoring lost and or reduced P-gp function (exofection) to sustain pregnancy homeostasis. A similar loss of P-gp at the blood brain barrier (BBB) contributes to impaired amyloid-{beta} (A{beta}) clearance and neuroinflammation in Alzheimers disease. We investigated whether CTC-EV-mediated exofection could restore P-gp function in human brain endothelial cells (hBECs) and enhance A{beta} clearance under inflammatory and neurodegenerative conditions. MethodsCTC-EVs were isolated and characterized by nanoparticle tracking analysis and western blotting for P-gp and EV markers. Transcriptomic profiling of CTC-EVs identified enrichment of transporter-related genes, including solute carriers and ABC transporters, along with inflammatory mediators. Network analysis revealed coordinated modules linking EV cargo to transporter regulation, endocytosis/trafficking pathways, and inflammatory remodeling processes converging on BBB efflux activity. hBECs were exposed to LPS (500 ng/mL, 48 h) with or without CTC-EVs. P-gp expression was assessed by immunofluorescence (mean fluorescence intensity, MFI) and western blotting, while functional efflux was measured using Calcein-AM assays. A{beta} oligomer transport was evaluated using a transwell hBEC model. In vivo, 3xTg-AD mice received intravenous CTC-EVs (1x10L/day for 5 days), followed by assessment of P-gp expression, A{beta} burden, and neuroinflammatory markers. Pharmacokinetic studies in P-gp knockout mice were conducted to confirm functional transporter recovery. ResultsLPS exposure significantly reduced P-gp expression in hBECs (41.3% decrease in MFI, p=0.0084), which was restored by CTC-EVs (46.7% increase vs. LPS, p=0.0121). Exofection increased P-gp by a 2.1-fold following EV treatment as determined by western blot. Functional assays demonstrated enhanced efflux, with a 38.5% reduction in intracellular Calcein fluorescence (p<0.001). Network-informed mechanisms supported coordinated regulation of transporter and trafficking pathways. CTC-EVs improved A{beta} transport across inflamed hBEC monolayers. In vivo, EV-treated 3xTg-AD mice exhibited increased P-gp expression in the frontal cortex (38.6%) and hippocampus (42.1%), reduced A{beta} plaque burden (27.9%), and decreased inflammatory markers (IL-1{beta} and TNF-, p<0.05). In P-gp knockout mice, EVs reduced brain drug accumulation by 22.4% (p=0.032), confirming restoration of transporter function. ConclusionCTC derived EVs are natural carriers of functional transporter proteins and restore efflux capacity in compromised endothelial barriers. Integration of transcriptomic and network analyses highlights coordinated regulation of transporter, trafficking, and inflammatory pathways underlying exofection. This reproductive biology inspired strategy offers a promising therapeutic approach for enhancing A{beta} clearance and mitigating neuroinflammation in Alzheimers disease.

Alzheimers disease (AD), the most prevalent neurodegenerative disorder, is marked by the accumulation of amyloid-{beta} (A{beta}) plaques. Although cerebral A{beta} positron emission tomography (A{beta}-PET) remains the gold standard for assessing cerebral A{beta} burden, its clinical utility is hindered by cost, radiation exposure, and limited availability. Plasma biomarkers serve as promising non-invasive predictors of cerebral A{beta} burden, but reliance on a single marker often leads to suboptimal predictive performance. To address this, we proposed a multimodal machine learning strategy that integrates readily accessible and non-invasive features--such as plasma biomarkers, structural magnetic resonance imaging (sMRI)-derived atrophy measures, diffusion tensor imaging (DTI)-based structural connectomes (SCs), and genetic risk profiles--to predict cerebral A{beta} burden and evaluate the relative contribution of each modality to predictive performance. Specifically, a random forest regressor was trained using data from the Alzheimers Disease Neuroimaging Initiative (ADNI; n = 150) and evaluated with leave-one-out cross-validation. Our results showed that integrating multimodal features improves the predictive power on cerebral amyloid burden: while the baseline model using plasma and clinical variables alone achieved an R{superscript 2} of 0.52, adding neuroimaging and apolipoprotein E (APOE) genotype features improved performance (R{superscript 2} = 0.617), and replacing APOE with polygenic risk scores (PRS) further enhanced accuracy (R{superscript 2} = 0.637). The predictive value of multimodal integration was also replicated in an independent cohort (SILCODE; n = 101). Moreover, a multiclass classifier trained with the same multimodal features achieved high accuracy in distinguishing clinical stages of A{beta} burden--normal controls (NC), mild cognitive impairment (MCI), and Alzheimers disease (AD)--with area under the curve (AUC) values of 0.86, 0.77, and 0.93, respectively. These findings highlight the value of combining plasma, imaging, and genetic data to non-invasively estimate cerebral A{beta} burden, offering a potential alternative to PET imaging for early AD risk assessment.

BackgroundCerebral microinfarcts often occur as a result of microvessel occlusion and are prevalent among dementia patients and the aging population. Detailed studies on the timecourse of microvascular occlusions indicate that endogenous mechanisms exist to re-canalize occluded vessels. One recently discovered mechanism is angiophagy, where vessels engulf and expel microemboli, thus mitigating damage caused by micro-occlusions. While several previous studies have shown that angiophagy occurs in rodent models, the frequency and timing of this process is not well characterized. In addition, there is limited data on the impact of aging on angiophagy, or the occurrence of this process in clinically relevant diseases such as Alzheimers disease. MethodsTo further study the timecourse of angiophagy, we induced micro-occlusions in young, aged and 3xTg Alzheimers mice via injection of 20m microspheres into the carotid artery. Mice were sacrificed on day 3, 7 or 14 and the brains were processed for brain-wide localization of microspheres and quantification of angiophagy. ResultsWe found the largest number of microspheres in the neocortex, yet when accounting for region size, microspheres were more evenly distributed across brain regions. When quantifying angiophagy in young non-diseased mice, we found that approximately 43% of microspheres had extravasated from the vessel by day 14. This process was delayed in aged mice, with only 10% of microspheres extravasated by day 14. Moreover, in young 3xTg Alzheimers mice, we found the rate of angiophagy to be more efficient at day 14 compared to non-transgenic controls, with 47% and 43% of microspheres extravasated, respectively. A similar trend was observed in aged Alzheimers mice, in which 38% of microspheres were extravasated by day 14 in 3xTg mice, compared to only 30% in non-transgenic controls. ConclusionsTaken together, we find that while aging impairs the process of angiophagy, Alzheimers mice exhibit a paradoxical increase in the rate of microsphere extravasation. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=90 SRC="FIGDIR/small/679680v1_ufig1.gif" ALT="Figure 1"> View larger version (17K): org.highwire.dtl.DTLVardef@760ec2org.highwire.dtl.DTLVardef@c2e2caorg.highwire.dtl.DTLVardef@b76011org.highwire.dtl.DTLVardef@1040eec_HPS_FORMAT_FIGEXP M_FIG C_FIG

Patients with Alzheimers disease (AD) and clinically overlapping neurodegenerative diseases are classified molecularly using the A/T/N classification system. Apart from fluid biomarkers and structural MRI, the three-dimensional A/T/N system incorporates characteristic features from {beta}-amyloid-PET (A), tau-PET (T), and FDG-PET (N). We evaluated if dynamic features of tau-PET with [18F]PI-2620 allow assessment of A/T/N in individual patients using a single imaging session. Cortical tissue clearance (K2a) of [18F]PI-2620 was validated as a surrogate of the {beta}-amyloid status against {beta}-amyloid-PET and cerebrospinal fluid (CSF) A{beta}42/40 ratio, demonstrating remarkable positive (91.5%) and negative (95.1%) predictive values at an AUC of 0.99 (P<0.0001). K2a outperformed cortical tau burden as a surrogate for {beta}-amyloid status in 47 participants with a clinical diagnosis of probable AD (3/4-repeat(R)-tauopathy) and 82 {beta}-amyloid-negative patients with primary 4R-tauopathies. Perfusion-like [18F]PI-2620 images (R1) were validated as a surrogate marker for neuronal injury, exhibiting strong quantitative and visual correlations with FDG-PET and early-phase {beta}-amyloid-PET, as well as with volumetric MRI and CSF total tau levels. Composite quantitative A/T/N indices facilitated personalized staging along temporal disease trajectories. Our results suggest that [18F]PI-2620 imaging has the potential to facilitate the assessment of region and stage dependent PET-based A/T/N during a single dynamic PET session. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=114 SRC="FIGDIR/small/25320240v1_ufig1.gif" ALT="Figure 1"> View larger version (43K): org.highwire.dtl.DTLVardef@25229forg.highwire.dtl.DTLVardef@3ff0eorg.highwire.dtl.DTLVardef@5df95forg.highwire.dtl.DTLVardef@19eef09_HPS_FORMAT_FIGEXP M_FIG C_FIG

Alzheimers disease (AD) is the leading cause of dementia, with metabolic dysfunction seen years before the emergence of clinical symptoms. Increasing evidence suggests a role for primary and secondary bile acids, the end-product of cholesterol metabolism, influencing pathophysiology in AD. In this study, we analyzed transcriptomes from 2114 post-mortem brain samples from three independent cohorts and identified that the genes involved in alternative bile acid synthesis pathway was expressed in brain compared to the classical pathway. These results were supported by targeted metabolomic analysis of primary and secondary bile acids measured from post-mortem brain samples of 111 individuals. We reconstructed brain region-specific metabolic networks using data from three independent cohorts to assess the role of bile acid metabolism in AD pathophysiology. Our metabolic network analysis suggested that taurine transport, bile acid synthesis and cholesterol metabolism differed in AD and cognitively normal individuals. Using the brain transcriptional regulatory network, we identified putative transcription factors regulating these metabolic genes and influencing altered metabolism in AD. Intriguingly, we find bile acids from the brain metabolomics whose synthesis cannot be explained by enzymes we find in the brain, suggesting they may originate from an external source such as the gut microbiome. These findings motivate further research into bile acid metabolism and transport in AD to elucidate their possible connection to cognitive decline.

Single-value scores reflecting the deviation from (FADE score) or similarity with (SAME score) prototypical novelty-related and memory-related functional magnetic resonance imaging (fMRI) activation patterns in young adults have been proposed as imaging biomarkers of healthy neurocognitive aging. Here, we tested the utility of these scores as potential diagnostic and prognostic markers in Alzheimers disease (AD) and risk states like mild cognitive impairment (MCI) or subjective cognitive decline (SCD). To this end, we analyzed subsequent memory fMRI data from individuals with SCD, MCI, and AD dementia as well as healthy controls (HC) and first-degree relatives of AD dementia patients (AD-rel) who participated in the multi-center DELCODE study (N = 468). Based on the individual participants whole-brain fMRI novelty and subsequent memory responses, we calculated the FADE and SAME scores and assessed their association with AD risk stage, neuropsychological test scores, CSF amyloid positivity, and ApoE genotype. Memory-based FADE and SAME scores showed a considerably larger deviation from a reference sample of young adults in the MCI and AD dementia groups compared to HC, SCD and AD-rel. In addition, novelty-based scores significantly differed between the MCI and AD dementia groups. Across the entire sample, single-value scores correlated with neuropsychological test performance. The novelty-based SAME score further differed between A{beta}-positive and A{beta}-negative individuals in SCD and AD-rel, and between ApoE {varepsilon}4 carriers and non-carriers in AD-rel. Hence, FADE and SAME scores are associated with both cognitive performance and individual risk factors for AD. Their potential utility as diagnostic and prognostic biomarkers warrants further exploration, particularly in individuals with SCD and healthy relatives of AD dementia patients.