Amyloid Pathology Research Articles

Abstract TP398: RNS60 Substantially Reduces Early Vasogenic Edema, Mitigates Infarct Area, and Decreases Expression of HIF1α Four Days Post-Ischemic Stroke

Introduction: RNS60 is a proprietary 0.9% saline solution with an elevated oxygen concentration. Previously, we showed that 13 days of daily RNS60 treatment after transient middle cerebral artery occlusion (tMCAo) stroke reduced brain pathology (e.g., infarction, amyloid pathology, neuronal death, microglial activation, and white matter damage) while increasing microvascular perfusion and memory (Baena Caldas et al. 2024). Here, we examine earlier brain-protective effects of daily RNS60 treatment 4 days after stroke. Methods: Male C57BL/6J mice, 3-4 months old, were randomly divided into sham surgery or unilateral 60-minute tMCAo. Each group was subdivided into three treatment arms: an experimental arm receiving daily intraperitoneal injections of 0.2 mL of stabilized RNS60, and control arms of pressurized normal saline with the same oxygen content as RNS60 (PNS60) or normal saline (NS). Injections began 2 hours after stroke, once daily for 3 days. An additional group without treatment was used as a control. Treatment group assignments were blinded throughout the study. On day 4, mice from each group were euthanized to assess infarct volume using TTC staining, or were perfused with 4% PFA to perform immunohistochemistry. Results: Four days after ischemic stroke, daily injections of RNS60 treatment significantly reduced early post-stroke vasogenic edema by 41% and infarct size by 39% compared to controls. These RNS60 brain-protective effects were related to decreased expression of hypoxia-inducible factor 1α (HIF1α), suggesting that RNS60 treatment may reduce hypoxia. Conclusion: RNS60-treated mice exhibit early and long-term significant brain protection after ischemic stroke associated with decreased expression of HIF1α, suggesting reduced hypoxia in the ischemic brain. Ongoing studies aim to identify the effect of RNS60 on blood brain barrier integrity to further elucidate the underlying molecular mechanism.

Basal forebrain global functional connectivity is preserved in asymptomatic presenilin-1 E280A mutation carriers: Results from the Colombia cohort.

Imaging studies showed early atrophy of the cholinergic basal forebrain in prodromal sporadic Alzheimer's disease and reduced posterior basal forebrain functional connectivity in amyloid positive individuals with subjective cognitive decline. Similar investigations in familial cases of Alzheimer's disease are still lacking. To test whether presenilin-1 E280A mutation carriers have reduced basal forebrain functional connectivity and whether this is linked to amyloid pathology. This is a cross-sectional study that analyzes baseline functional imaging data. We obtained data from the Colombia cohort Alzheimer's Prevention Initiative Autosomal-Dominant Alzheimer's Disease Trial. We analyzed data from 215 asymptomatic subjects carrying the presenilin-1 E280A mutation [64% female; 147 carriers (M = 35 years), 68 noncarriers (M = 40 years)]. We extracted functional magnetic resonance imaging data using seed-based connectivity analysis to examine the anterior and posterior subdivisions of the basal forebrain. Subsequently, we performed a Bayesian Analysis of Covariance to assess the impact of carrier status on functional connectivity in relation to amyloid positivity. For comparison, we also investigated hippocampus connectivity. We found no effect of carrier status on anterior (Bayesian Factor10 = 1.167) and posterior basal forebrain connectivity (Bayesian Factor10 = 0.033). In carriers, we found no association of amyloid positivity with basal forebrain connectivity. We falsified the hypothesis of basal forebrain connectivity reduction in preclinical mutation carriers with amyloid pathology. If replicated, these findings may not only confirm a discrepancy between familial and sporadic Alzheimer's disease, but also suggest new potential targets for future treatments.

Core blood biomarkers of Alzheimer's disease: A single-center real-world performance study.

The new criteria for Alzheimer's disease pave the way for the introduction of core blood biomarkers of Alzheimer's disease (BBAD) into clinical practice. However, this depends on the demonstration of sufficient accuracy and robustness of BBADs in the intended population. To assess the diagnostic performance of core BBADs in our memory clinic, comparing them with cerebrospinal fluid (CSF) analysis. Real-world cross-sectional observational study. Memory Clinic of Fondazione IRCCS "San Gerardo dei Tintori," Monza, Italy. n = 102 consecutive outpatients (mean age: 71.0 ± 7.6 years) with cognitive impairment undergoing routine lumbar puncture. CSF Aβ40, Aβ42, tTau, and pTau181 levels were measured. Plasma biomarkers were evaluated using Lumipulse® G600II. Logistic regression and Receiver Operating Characteristic (ROC) analysis were used to assess biomarker performance. The diagnosis of Alzheimer's disease was based on CSF Aβ42/40 ratio. Plasma pTau217 demonstrated the highest diagnostic accuracy (AUC=0.91), followed by pTau181 (AUC=0.88) and Aβ42/40 (AUC=0.83). In robustness analyses, only pTau217 and pTau181 performance remained consistent, while that of Aβ42/40 ratio declined with added random variability. pTau217 significantly outperformed other BBAD, with the exception of pTau181. pTau BBAD were significant predictors of baseline Mini-Mental State Examination scores. Plasma pTau217, measured with Lumipulse®, is a robust and reliable BBAD for detecting amyloid pathology in a memory clinic setting, offering a practical and less invasive alternative to traditional CSF testing.

Advancing Alzheimer's disease pharmacotherapy: efficacy of glucocorticoid modulation with dazucorilant (CORT113176) in preclinical mouse models.

Exposure to chronic stress and high levels of glucocorticoid hormones in adulthood has been associated with cognitive deficits and increased risk of Alzheimer's disease (AD). Dazucorilant has recently emerged as a selective glucocorticoid receptor (NR3C1) modulator, exhibiting efficacy in counteracting amyloid-β toxicity in an acute model of AD. We aim to assess the therapeutic potential of dazucorilant in reversing amyloid and tau pathologies through the inhibition of glucocorticoid receptor pathological activity, and providing additional evidence for its consideration in AD treatment. The efficacy of dazucorilant was evaluated in two transgenic mouse models of amyloid pathology. The slowly progressing J20 and the aggressively pathological 5xFAD mice. Behavioural analysis was conducted to evaluate welfare, cognitive performances and anxiety levels. The activity of the glucocorticoid receptor system, neuroinflammation, amyloid burden and tau phosphorylation were examined in hippocampi. In both AD models, chronic treatment with dazucorilant improved working and long-term spatial memories along with the inhibition of glucocorticoid receptor-dependent pathogenic processes and the normalization of plasma glucocorticoid levels. Dazucorilant treatment also resulted in a reduction in tau hyperphosphorylation and amyloid production and aggregation. Additionally, dazucorilant seemed to mediate a specific re-localization of activated glial cells onto amyloid plaques in J20 mice, suggesting a restoration of physiological neuroinflammatory processes. Dazucorilant exhibited sustained disease-modifying effects in two AD models. Given that this compound has demonstrated safety and tolerability in human subjects, our results provide pre-clinical support for conducting clinical trials to evaluate its potential in AD.

Amyloid Targeting-Gold Nanoparticles-Assisted X-ray Therapy Rescues Islet β-Cells from Amyloid Fibrils and Restores Insulin Homeostasis.

Type-2-diabetes is a metabolic disorder where misfolding and oligomerization of islet amyloid polypeptide (IAPP) around islet-β cells oligomerizes and participates in the pathology. The oligomeric stage is toxic but transitory and leads to the formation of mature amyloid fibrils. The pathological specifics of mature amyloid fibrils are poorly understood. Here, we demonstrate that IAPP amyloids make a gel-like transition, increasing the viscosity of the local microenvironment and encasing and impeding islet-β cells in their ability to sense glucose and release insulin. Using dual-targeted gold nanoparticles (AuNPs) capped with amyloid-fragments of βCasein and anti-IAPP antibodies, we show that X-ray irradiation of AuNPs when bound to IAPP amyloids results in therapeutic remodelling of IAPP amyloids, a reduction in viscosity of the solution, and restoration of glucose/insulin homeostasis. This study establishes that mature IAPP amyloids can participate in the progressive pathology of type-2-diabetes by suppressing insulin responsiveness at the single islet-cell level. It also identifies a therapeutic model of reversal using AuNPs-mediated X-ray therapy, and this approach can be rationally expanded to other amyloid pathologies, such as Alzheimer's and Parkinson's diseases.

Plasma p-tau217 and p-tau217/Aβ1-42 are effective biomarkers for identifying CSF- and PET imaging-diagnosed Alzheimer's disease: Insights for research and clinical practice.

With the advancement of disease-modifying therapies for Alzheimer's disease (AD), validating plasma biomarkers against cerebrospinal fluid (CSF) and positron emission tomography (PET) standards is crucial in both research and real-world settings. We measured plasma phosphorylated tau (p-tau)217, p-tau181, amyloid beta (Aβ)1-40, Aβ1-42, and neurofilament light chain in research and real-world cohorts. Participants were categorized by brain amyloid status using US Food and Drug Administration/European Medicines Agency-approved CSF or PET methods. Plasma p-tau217 and p-tau217/Aβ1-42 demonstrated superior accuracy in detecting brain amyloid pathologies, with area under the curve from 0.94 to 0.97 in all cohorts. Specificity was lower in the real-world cohort but improved significantly by integrating demographic and clinical factors, aligning performance with research cohorts. Additionally, plasma biomarkers exhibited strong correlations with their CSF counterparts and PET standardized uptake value ratios, with significant associations in amyloid-positive participants. Plasma p-tau217 and p-tau217/Aβ1-42 are effective diagnostic tools. However, patient demographics, apolipoprotein E ε4 status, and cognitive condition must be considered to improve specificity in the clinical practice. Plasma phosphorylated tau (p-tau)217 and p-tau217/amyloid beta (Aβ)1-42 demonstrated exceptional accuracy (area under the curve: 0.94-0.97) in detecting brain amyloid pathologies across both research (Southern China Aging Brain Initiative [SCABI]-1, SCABI-2) and real-world clinical practice (RCP) cohorts. Incorporating patient-specific factors (sex, age, apolipoprotein E ε4, cognitive status) improved diagnostic specificity in the clinical RCP cohort, aligning its performance with that of research cohorts. Plasma biomarkers, particularly p-tau217 and their ratios, showed robust correlations with cerebrospinal fluid biomarkers and positron emission tomography amyloid standardized uptake value ratios, underscoring their value as non-invasive diagnostic alternatives. Plasma p-tau217 and p-tau217/Aβ1-42 proved highly effective in diagnosing amyloid burden, offering a practical solution to bridge research advancements with real-world clinical practice.

Oligodendrocytes in Alzheimer's disease pathophysiology.

Our understanding of Alzheimer's disease (AD) has transformed from a purely neuronal perspective to one that acknowledges the involvement of glial cells. Despite remarkable progress in unraveling the biology of microglia, astrocytes and vascular elements, the exploration of oligodendrocytes in AD is still in its early stages. Contrary to the traditional notion of oligodendrocytes as passive bystanders in AD pathology, emerging evidence indicates their active participation in and reaction to amyloid and tau pathology. Oligodendrocytes undergo a functional transition to a disease-associated state, engaging in immune modulation, stress responses and cellular survival. Far from being inert players, they appear to serve a dual role in AD pathogenesis, potentially offering defense mechanisms against pathology while also contributing to disease progression. This Review explores recent advancements in understanding the roles of oligodendrocytes and their myelin sheaths in the context of AD, shedding light on their complex interactions within the disease pathology.

Novel Monoclonal Antibodies for the Treatment of Alzheimers Disease using KISUNLA Drug

For persons with early-stage sympathetic Alzheimer's disease (AD), including those with mild cognitive impairment and mild congitive dementia stages of the disease with confirmed amyloid pathology, KISUNLA (donanemab-azbt) is a disease-modifying treatment. Nearly half of research participants finished their course of treatment with Kisunla within a year, making it the first and only amyloid plaque targeting medication that uses a limited duration treatment regimen based on amyloid plaque elimination. For those with early-stage sympathetic Alzheimer's disease who desperately require an efficient therapeutic alternative, Kisunla shows extremely significant results

Depressive Symptoms and Amyloid Pathology

Depressive symptoms are associated with cognitive decline in older individuals. Uncertainty about underlying mechanisms hampers diagnostic and therapeutic efforts. This large-scale study aimed to elucidate the association between depressive symptoms and amyloid pathology. To examine the association between depressive symptoms and amyloid pathology and its dependency on age, sex, education, and APOE genotype in older individuals without dementia. Cross-sectional analyses were performed using data from the Amyloid Biomarker Study data pooling initiative. Data from 49 research, population-based, and memory clinic studies were pooled and harmonized. The Amyloid Biomarker Study has been collecting data since 2012 and data collection is ongoing. At the time of analysis, 95 centers were included in the Amyloid Biomarker Study. The study included 9746 individuals with normal cognition (NC) and 3023 participants with mild cognitive impairment (MCI) aged between 34 and 100 years for whom data on amyloid biomarkers, presence of depressive symptoms, and age were available. Data were analyzed from December 2022 to February 2024. Amyloid-β1-42 levels in cerebrospinal fluid or amyloid positron emission tomography scans were used to determine presence or absence of amyloid pathology. Presence of depressive symptoms was determined on the basis of validated depression rating scale scores, evidence of a current clinical diagnosis of depression, or self-reported depressive symptoms. In individuals with NC (mean [SD] age, 68.6 [8.9] years; 5664 [58.2%] female; 3002 [34.0%] APOE ε4 carriers; 937 [9.6%] had depressive symptoms; 2648 [27.2%] had amyloid pathology), the presence of depressive symptoms was not associated with amyloid pathology (odds ratio [OR], 1.13; 95% CI, 0.90-1.40; P = .29). In individuals with MCI (mean [SD] age, 70.2 [8.7] years; 1481 [49.0%] female; 1046 [44.8%] APOE ε4 carriers; 824 [27.3%] had depressive symptoms; 1668 [55.8%] had amyloid pathology), the presence of depressive symptoms was associated with a lower likelihood of amyloid pathology (OR, 0.73; 95% CI 0.61-0.89; P = .001). When considering subgroup effects, in individuals with NC, the presence of depressive symptoms was associated with a higher frequency of amyloid pathology in APOE ε4 noncarriers (mean difference, 5.0%; 95% CI 1.0-9.0; P = .02) but not in APOE ε4 carriers. This was not the case in individuals with MCI. Depressive symptoms were not consistently associated with a higher frequency of amyloid pathology in participants with NC and were associated with a lower likelihood of amyloid pathology in participants with MCI. These findings were not influenced by age, sex, or education level. Mechanisms other than amyloid accumulation may commonly underlie depressive symptoms in late life.

Cerebral Microbleeds and Amyloid Pathology Estimates From the Amyloid Biomarker Study

Baseline cerebral microbleeds (CMBs) and APOE ε4 allele copy number are important risk factors for amyloid-related imaging abnormalities in patients with Alzheimer disease (AD) receiving therapies to lower amyloid-β plaque levels. To provide prevalence estimates of any, no more than 4, or fewer than 2 CMBs in association with amyloid status, APOE ε4 copy number, and age. This cross-sectional study used data included in the Amyloid Biomarker Study data pooling initiative (January 1, 2012, to the present [data collection is ongoing]). Data from 15 research and memory clinic studies were pooled and harmonized. Participants included individuals for whom data on age, cognitive status, amyloid status, and presence of CMBs were available. Data were analyzed from October 22, 2023, to April 26, 2024. The main outcomes were age, cognitive status, amyloid status and presence, location, and number of CMBs. Presence of amyloid pathology was determined based on 42 amino acid-long form of amyloid-β peptide (Aβ42) levels in cerebrospinal fluid or on amyloid-positron emission tomography. Presence and, in a subset, location (lobar vs deep) and number of CMBs were determined on magnetic resonance imaging (locally with visual rating). Among 4080 participants included in the analysis, the mean (SD) age was 66.5 (8.9) years, and 2241 (54.9%) were female. A total of 2973 participants had no cognitive impairment (cognitive unimpairment [CU]), and 1107 had mild cognitive impairment (MCI) or AD dementia (ADD). One thousand five hundred and thirteen participants (37.1%) had amyloid pathology, 1368 of 3599 (38.0%) with data available were APOE ε4 carriers, and 648 (15.9%) had CMBs. In the CU group, amyloid pathology and APOE ε4 copy number were not associated with presence of any, no more than 4, or fewer than 2 CMBs but were associated with increased odds of lobar CMBs (odds ratio [OR] for amyloid, 1.42 [95% CI, 1.20-1.69], P < .001; OR for 2 vs 0 alleles, 1.81 [95% CI, 1.19-2.74], P = .006; OR for 1 vs 0 alleles, 1.10 [95% CI, 0.83-1.46], P = .49; and OR for 2 vs 1 allele, 1.64 [95% CI, 0.90-2.97], P = .11; overall P = .02). In the MCI-ADD group, amyloid pathology was associated with presence of any CMBs (OR, 1.51 [95% CI, 1.17-1.96], P = .002), no more than 4 CMBs (OR, 1.44 [95% CI, 1.18-1.82], P = .002), and fewer than 2 CMBs (OR 1.34 [95% CI, 1.03-1.74], P = .03) but not lobar CMBs. APOE ε4 copy number was associated with presence of any (OR for 2 vs 0 alleles, 1.72 [95% CI, 0.88-3.35], P = .11; OR for 1 vs 0 alleles, 0.78 [95% CI, 0.59-1.04], P = .09; and OR for 2 vs 1 allele, 2.20 [95% CI, 1.32-3.67], P = .002; overall P < .001) and no more than 4 CMBs (OR for 2 vs 0 alleles, 1.31 [95% CI, 0.64-2.68], P = .45; OR for 1 vs 0 alleles, 0.75 [95% CI, 0.54-1.04], P = .08; and OR for 2 vs 1 allele, 1.76 [95% CI, 0.97-3.19], P = .06; overall P = .03) but not with fewer than 2 or lobar CMBs. Prevalence estimates of CMBs ranged from 6% at 50 years of age in a non-APOE ε4 allele carrier with no amyloid pathology and no cognitive impairment to 52% at 90 years of age in an APOE ε4 homozygote carrier with amyloid pathology and cognitive impairment. In this cross-sectional study of 4080 participants, prevalence estimates of CMBs were associated with amyloid status, APOE ε4 copy number, and age. CMB prevalence estimates may help inform safety evaluations for antiamyloid clinical trials.

APOE Christchurch enhances a disease-associated microglial response to plaque but suppresses response to tau pathology

BackgroundApolipoprotein E ε4 (APOE4) is the strongest genetic risk factor for late-onset Alzheimer’s disease (LOAD). A recent case report identified a rare variant in APOE, APOE3-R136S (Christchurch), proposed to confer resistance to autosomal dominant Alzheimer’s Disease (AD). However, it remains unclear whether and how this variant exerts its protective effects.MethodsWe introduced the R136S variant into mouse Apoe (ApoeCh) and investigated its effect on the development of AD-related pathology using the 5xFAD model of amyloidosis and the PS19 model of tauopathy. We used immunohistochemical and biochemical analysis along with single-cell spatial omics and bulk proteomics to explore the impact of the ApoeCh variant on AD pathological development and the brain’s response to plaques and tau.ResultsIn 5xFAD mice, ApoeCh enhances a Disease-Associated Microglia (DAM) phenotype in microglia surrounding plaques, and reduces plaque load, dystrophic neurites, and plasma neurofilament light chain. By contrast, in PS19 mice, ApoeCh suppresses the microglial and astrocytic responses to tau-laden neurons and does not reduce tau accumulation or phosphorylation, but partially rescues tau-induced synaptic and myelin loss. We compared how microglia responses differ between the two mouse models to elucidate the distinct DAM signatures induced by ApoeCh. We identified upregulation of antigen presentation-related genes in the DAM response in a PS19 compared to a 5xFAD background, suggesting a differential response to amyloid versus tau pathology that is modulated by the presence of ApoeCh. Bulk proteomics show upregulated mitochondrial protein abundance with ApoeCh in 5xFAD mice, but reductions in mitochondrial and translation associated proteins in PS19 mice.ConclusionsThese findings highlight the ability of the ApoeCh variant to modulate microglial responses based on the type of pathology, enhancing DAM reactivity in amyloid models and dampening neuroinflammation to promote protection in tau models. This suggests that the Christchurch variant's protective effects likely involve multiple mechanisms, including changes in receptor binding and microglial programming.Graphical

Deletion of Murine APP Aggravates Tau and Amyloid Pathologies in the 5xFADXTg30 Alzheimer’s Disease Model

Deletion of Murine APP Aggravates Tau and Amyloid Pathologies in the 5xFADXTg30 Alzheimer’s Disease Model

Microglial double stranded DNA accumulation induced by DNase II deficiency drives neuroinflammation and neurodegeneration

BackgroundDeoxyribonuclease 2 (DNase II) is pivotal in the clearance of cytoplasmic double stranded DNA (dsDNA). Its deficiency incurs DNA accumulation in cytoplasm, which is a hallmark of multiple neurodegenerative diseases. Our previous study showed that neuronal DNase II deficiency drove tau hyperphosphorylation and neurodegeneration (Li et al., Transl Neurodegener 13:39, 2024). Although it has been verified that DNase II participates in type I interferons (IFN-I) mediated autoinflammation and senescence in peripheral systems, the role of microglial DNase II in neuroinflammation and neurodegenerative diseases such as Alzheimer’s disease (AD) is still unknown.MethodsThe levels of microglial DNase II in triple transgenic AD mice (3xTg-AD) were measured by immunohistochemistry. The cognitive performance of microglial DNase II deficient WT and AD mice was determined using the Morris water maze test, Y-maze test, novel object recognition test and open filed test. To investigate the impact of microglial DNase II deficiency on microglial morphology, cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway and IFN-I pathway, neuroinflammation, synapses loss, amyloid pathology and tauopathy, the levels of cGAS-STING and IFN-I pathway related protein, gliosis and proinflammatory cytokines, synaptic protein, complement protein, Aβ levels, phosphorylated tau in the brains of the microglial DNase II deficient WT and AD mice were evaluated by immunolabeling, immunoblotting, q-PCR or ELISA.ResultsWe found that the levels of DNase II were significantly decreased in the microglia of 3xTg-AD mice. Microglial DNase II deficiency altered microglial morphology and transcriptional signatures, activated the cGAS-STING and IFN-I pathway, initiated neuroinflammation, led to synapse loss via complement-dependent pathway, increased Aβ levels and tauopathy, and induced cognitive decline.ConclusionsOur study shows the effect of microglial DNase II deficiency and cytoplasmic accumulated dsDNA on neuroinflammation, and reveals the initiatory mechanism of AD pathology, suggesting that DNase II is a potential target for neurodegenerative diseases.

Novel synaptic markers predict early tau pathology and cognitive deficit in an asymptomatic population at risk of Alzheimer's disease.

Cognitive dysfunction in Alzheimer's disease (AD) correlates closely with pathology in the neuronal microtubule-associated protein tau. Tau pathology may spread via neural synapses. In a population of cognitively unimpaired elderly at elevated risk of AD, we investigated four cerebrospinal (CSF) markers of synaptic dysfunction and degeneration. Three of these (SYT1, SNAP25, and ADAM23) are derived from pre-synaptic structures, while ADAM22 reflects post-synaptic changes. All four markers correlated strongly with tau protein measures. In statistical models, SYT1 accounted for more than half the total variance in both total- and P(181)-tau levels. Observed correlations with CSF levels of Alzheimer amyloid-β (Aβ42) were somewhat weaker. In longitudinal data, baseline levels of ADAM22 and ADAM23 robustly predicted increase over time in both total- and P-tau. CSF SYT1 levels also correlated with PET image uptake of tau and (at a trend level) Aβ in areas of interest for early AD pathology. CSF SYT1 and SNAP25 levels correlated inversely with a global psychometric score and several of its domain subscales. In quantitative trait loci analyses, all four synaptic markers were associated with at least one AD genetic risk locus. Upon "staging" participants by their evidence of amyloid and tau pathology (A/T/N framework), the CSF synaptic markers were unexpectedly reduced in participants with CSF evidence of amyloid but not tau pathology. They were clearly elevated, however, in the CSF of persons with indications of both tau and amyloid pathology. These observations provide evidence for clear pre-synaptic degeneration in cognitively unimpaired persons with biomarker evidence of early AD pathology.

Differences of longitudinal plasma biomarkers between single memory domain and multidomain subject cognitive decline: Evidence from SILCODE.

Plasma biomarkers demonstrated potential in identifying amyloid pathology in early Alzheimer's disease. Different subtypes of subjective cognitive decline (SCD) may lead to different cognitive impairment conversion risks. To investigate the differences of plasma biomarkers in SCD subtypes individuals, which were unclear. The 347 individuals were involved, including 93 normal controls (NC), 76 single memory domain SCD (sd-SCD), 79 multidomain SCD (md-SCD), 55 mild cognitive impairment and 44 dementia. We investigated plasma biomarkers (Aβ42/40, p-tau181, p-tau217, NfL, and GFAP) and neuropsychological scales in the baseline and follow-up. The Kaplan-Meier survival analysis and Cox proportional hazards model were performed to investigate the risk of cognitive decline conversion. The t-test, Mann-Whitney U and multiple linear regression analysis were employed to evaluate the rate of change and correlation between PET-SUVR and plasma biomarker change. In cognitively normal subjects, md-SCD exhibited lower Aβ42/40 and higher p-tau181 and p-tau217 levels. Kaplan-Meier survival analysis revealed that md-SCD group exhibited a higher risk of cognitive decline conversion compared to NC and sd-SCD. Within SCD subgroups, those with positive GFAP status showed higher conversion risk than negative. In the Cox model, the risk of conversion in the md-SCD group was 2.77 times higher than sd-SCD. The md-SCD group demonstrated a faster rate of Aβ42/40 decline than sd-SCD. The study utilized plasma biomarkers to highlight the significance of staging in SCD. In cognitively normal subjects, md-SCD presents a higher risk of cognitive decline than sd-SCD, providing a valuable reference and convenient tool for early identification of individuals at risk for AD.

The etiology and prevention of early-stage tau pathology in higher cortical circuits: Insights from aging rhesus macaques.

Aging rhesus macaques provide a unique model for learning how age and inflammation drive early-stage pathology in sporadic Alzheimer's disease, and for testing potential therapeutics. Unlike mice, aging macaques have extensive association cortices and inflammatory signaling similar to humans, are apolipoprotein E ε4 homozygotes, and naturally develop tau and amyloid pathology with marked cognitive deficits. Importantly, monkeys provide the unique opportunity to study early-stage, soluble hyperphosphorylated tau (p-tau), including p-tau217. As soluble p-tau is rapidly dephosphorylated post mortem, it is not captured in human brains except with biopsy material. However, new macaque data show that soluble p-tau is toxic to neurons and capable of seeding across cortical circuits. Extensive evidence indicates that age-related inflammatory signaling contributes to calcium dysregulation, which drives tau hyperphosphorylation and amyloid beta generation. Pharmacological studies in aged macaques suggest that inhibiting inflammation and restoring calcium regulation can reduce tau hyperphosphorylation with minimal side effects, appropriate for potential preventive therapeutics. HIGHLIGHTS: Aging monkeys provide a unique window into early stage, soluble phosphorylated tau (p-tau). Inflammation with advancing age leads to calcium dysregulation, p-tau, and amyloid beta (Aβ). Macaque research shows p-tau undergoes transsynaptic seeding early in the cortex. p-tau traps amyloid precursor protein-containing endosomes, which may increase Aβ and drive vicious cycles. Restoring calcium regulation in cortex reduced p-tau217 levels in aged macaques.

Cerebromicrovascular mechanisms contributing to long COVID: implications for neurocognitive health.

Long COVID (also known as post-acute sequelae of SARS-CoV-2 infection [PASC] or post-COVID syndrome) is characterized by persistent symptoms that extend beyond the acute phase of SARS-CoV-2 infection, affecting approximately 10% to over 30% of those infected. It presents a significant clinical challenge, notably due to pronounced neurocognitive symptoms such as brain fog. The mechanisms underlying these effects are multifactorial, with mounting evidence pointing to a central role of cerebromicrovascular dysfunction. This review investigates key pathophysiological mechanisms contributing to cerebrovascular dysfunction in long COVID and their impacts on brain health. We discuss how endothelial tropism of SARS-CoV-2 and direct vascular infection trigger endothelial dysfunction, impaired neurovascular coupling, and blood-brain barrier disruption, resulting in compromised cerebral perfusion. Furthermore, the infection appears to induce mitochondrial dysfunction, enhancing oxidative stress and inflammation within cerebral endothelial cells. Autoantibody formation following infection also potentially exacerbates neurovascular injury, contributing to chronic vascular inflammation and ongoing blood-brain barrier compromise. These factors collectively contribute to the emergence of white matter hyperintensities, promote amyloid pathology, and may accelerate neurodegenerative processes, including Alzheimer's disease. This review also emphasizes the critical role of advanced imaging techniques in assessing cerebromicrovascular health and the need for targeted interventions to address these cerebrovascular complications. A deeper understanding of the cerebrovascular mechanisms of long COVID is essential to advance targeted treatments and mitigate its long-term neurocognitive consequences.

Pharmacological enhancement of slow-wave activity at an early disease stage improves cognition and reduces amyloid pathology in a mouse model of Alzheimer's disease.

Improving sleep in murine Alzheimer's disease (AD) is associated with reduced brain amyloidosis. However, the window of opportunity for successful sleep-targeted interventions, regarding the reduction in pathological hallmarks and related cognitive performance, remains poorly characterized. Here, we enhanced slow-wave activity (SWA) during sleep via sodium oxybate (SO) oral administration for 2 weeks at early (6 months old) or moderately late (11 months old) disease stages in Tg2576 mice and evaluated resulting neuropathology and behavioral performance. We observed that the cognitive performance of 6-month-old Tg2576 mice significantly improved upon SO treatment, whereas no change was observed in 11-month-old mice. Histochemical assessment of amyloid plaques demonstrated that SO-treated 11-month-old Tg2576 mice had significantly less plaque burden than placebo-treated ones, whereas ELISA of insoluble protein fractions from brains of 6-month-old Tg2576 mice indicated lower Aβ-42/Aβ-40 ratio in SO-treated group vs. placebo-treated controls. Altogether, our results suggest that SWA-dependent reduction in brain amyloidosis leads to alleviated behavioral impairment in Tg2576 mice only if administered early in the disease course, potentially highlighting the key importance of early sleep-based interventions in clinical cohorts.

Temporal modeling and AT profiles in the early phase of Alzheimer's disease

Background Identifying markers that have predictive value for disease progression and clinical manifestations, such as mild cognitive impairment (MCI), is important to detect Alzheimer's disease (AD) early. Objective In this study, we combined biomarkers from amyloid and tau pathologies (AT profiles) with the prediction of diagnosis and the temporal evolution of clinical symptoms. Methods Multiple disease progression models were developed through supervised and unsupervised techniques via a two-stage data-driven approach. Models whose natural histories most closely resembled the diagnostic predictions were selected. Finally, various hypotheses regarding the progression of cognitive decline were tested using longitudinal patient data and AT profiles. Results At baseline, 22.5% of the cognitively unimpaired (CU) individuals and 46.2% of the CU converters (who progressed to MCI during the first four years) in the studied population had amyloid pathology (A+). Only a small subset of neuropsychological measures was used to predict cognitive decline and its timeline. The study revealed that amyloid pathology occurred approximately 5 years after cognitive decline in the population under investigation. Additionally, patients who were A+ at baseline experienced a more accelerated progression toward cognitive decline than those who were not (A−). Conclusions Based on the proposed natural histories and cross-sectional and longitudinal analysis of AD markers, the results indicate that only a single cerebrospinal fluid sample is necessary during the early phase of AD. The progression from CU to MCI and its timeline can be predicted exclusively through neuropsychological measures.

Alzheimer's disease risk ABCA7 p.A696S variant disturbs the microglial response to amyloid pathology in mice.

The adenosine triphosphate-binding cassette transporter A7 (ABCA7) gene is ranked as one of the top susceptibility loci for Alzheimer's disease (AD). While ABCA7 mediates lipid transport across cellular membranes, ABCA7 loss of function has been shown to exacerbate amyloid-β (Aβ) pathology and compromise microglial function. Our family-based study uncovered an extremely rare ABCA7 p.A696S variant that was substantially segregated with the development of AD in 3 African American families. Using the knockin mouse model, we investigated the effects of ABCA7-A696S substitution on amyloid pathology and brain immune response in 5xFAD transgenic mice. Importantly, our study demonstrated that ABCA7-A696S substitution reduces amyloid plaque-associated microgliosis and increases dystrophic neurites around amyloid deposits compared to control mice. We also found increased X-34-positive amyloid plaque burden in 5xFAD mice with ABCA7-A696S substitution, while there was no evident difference in insoluble Aβ levels between mouse groups. Thus, ABCA7-A696S substitution may disrupt amyloid compaction resulting in aggravated neuritic dystrophy due to insufficient microglia barrier function. In addition, we observed that ABCA7-A696S substitution disturbs the induction of proinflammatory cytokines interleukin 1β and interferon γ in the brains of 5xFAD mice, although some disease-associated microglia gene expression, including Trem2 and Tyrobp, are upregulated. Lipidomics also detected higher total lysophosphatidylethanolamine levels in the brains of 5xFAD mice with ABCA7-A696S substitution than controls. These results suggest that ABCA7-A696S substitution might compromise the adequate innate immune response to amyloid pathology in AD by modulating brain lipid metabolism, providing novel insight into the pathogenic mechanisms mediated by ABCA7. ONE SENTENCE SUMMARY: A rare Alzheimer's disease risk ABCA7 p.A696S variant compromises microglial response to amyloid pathology.