Publications by authors named "Nesrine Rahmouni"

In this longitudinal brain imaging study, we aimed to characterize hippocampal tau accumulation and subfield atrophy relative to cortical amyloid-β and memory performance. We measured tau-PET in regions associated with Braak stages I to VI, global amyloid-PET burden, hippocampal subfield volumes and memory assessments from 173 participants aged 55-85. Eighty-six of these participants were tested again two years later.

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Article Synopsis
  • Recent advancements in Alzheimer's treatment now require verification of amyloid-β pathology using PET scans or cerebrospinal fluid, but blood tests could simplify this process.* -
  • A study involving nearly 7,000 individuals identified that the plasma biomarker p-tau217 can reliably indicate amyloid-β pathology, especially in patients with probable Alzheimer’s dementia.* -
  • The findings suggest that combining p-tau217 results with clinical assessments may allow for accurate diagnoses without the need for more invasive PET or CSF tests.*
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Background: Blood-based disease staging across the Alzheimer's disease (AD) continuum holds the promise to identify individuals that profit from disease-modifying therapies. We set out to identify Braak V (Braak V and/or VI) tau PET-positive individuals within amyloid-β (Aβ)-positive individuals using plasma biomarkers.

Methods: In this cross-sectional study, we assessed 289 individuals from the TRIAD cohort and 306 individuals from the WRAP study across the AD continuum.

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  • The study aimed to compare the in vitro binding characteristics of three radiotracers ([F]flortaucipir, [F]MK6240, [F]PI2620) in postmortem brain samples from Alzheimer’s disease (AD) and control groups.
  • Significant differences in tracer binding were found in the whole-brain hemisphere, prefrontal cortex, and hippocampus between AD and control tissues, with [F]MK6240 and [F]PI2620 showing better performance in differentiating AD cases.
  • The results indicate that [F]MK6240 and [F]PI2620 have higher selectivity and binding to AD tissues compared to [F]flortaucipir,
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Background And Purpose: This study was undertaken to compare the performance of plasma p-tau181 with that of [F]fluorodeoxyglucose (FDG) positron emission tomography (PET) in the identification of early biological Alzheimer disease (AD).

Methods: We included 533 cognitively impaired participants from the Alzheimer's Disease Neuroimaging Initiative. Participants underwent PET scans, biofluid collection, and cognitive tests.

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Positron Emission Tomography (PET) ligands have advanced Alzheimer's disease (AD) diagnosis and treatment. Using autoradiography and cryo-EM, we identify AD brain tissue with elevated tau burden, purify filaments, and determine the structure of second-generation high avidity PET ligand MK-6240 at 2.31 Å resolution, which bound at a 1:1 ratio within the cleft of tau paired-helical filament (PHF), engaging with glutamine 351, lysine 353, and isoleucine 360.

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In Alzheimer's disease (AD), neuropsychiatric symptoms (NPS) correlate with tau deposition in the brain. Here, we investigated the association of PET-based Braak stages with NPS and assessed whether they predict annual changes in NPS. We evaluated 231 individuals in the aging and AD continuum.

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Previous studies have shown that glial and neuronal changes may trigger synaptic dysfunction in Alzheimer's disease(AD). However, the link between glial and neuronal markers and synaptic abnormalities in the living brain is poorly understood. Here, we investigated the association between biomarkers of astrocyte and microglial reactivity and synaptic dysfunction in 478 individuals across the aging and AD spectrum from two cohorts with available CSF measures of amyloid-β(Aβ), phosphorylated tau(pTau181), astrocyte reactivity(GFAP), microglial activation(sTREM2), and synaptic biomarkers(GAP43 and neurogranin).

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Background: Females represent approximately 70% of the Alzheimer's disease (AD) cases and the literature has proposed a connection between the decreased estrogen levels during menopause and an increased AD risk. Previous investigations have predominantly focused on assessing how hormone therapy (HT) affects the likelihood of AD development and cognitive deterioration. However, as the research framework has shifted toward a biomarker-defined AD and alterations in specific biomarkers could take place years before cognitive decline becomes discernible, it is crucial to examine how HT influences AD biomarkers.

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The molecular mechanisms underlying neuronal dysfunction in Alzheimer's disease (AD) remain uncharacterized. Here, we identify genes, molecular pathways and cellular components associated with whole-brain dysregulation caused by amyloid-beta (Aβ) and tau deposits in the living human brain. We obtained resting-state functional MRI (rs-fMRI), Aβ- and tau-PET for 47 cognitively unimpaired and 16 AD participants from the Translational Biomarkers in Aging and Dementia cohort.

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Article Synopsis
  • Plasma p-tau217 and Tau-PET are effective biomarkers for predicting cognitive decline in individuals without cognitive impairment, showing similar effectiveness in testing.
  • A study with 1534 participants demonstrated that using a combination of both biomarkers provided better predictive power than using either one alone.
  • Sequential testing of plasma p-tau217 followed by Tau-PET significantly reduces the number of participants needed in clinical trials for preclinical Alzheimer's disease, streamlining the research process.
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Alzheimer's disease (AD) is a brain network disorder where pathological proteins accumulate through networks and drive cognitive decline. Yet, the role of network connectivity in facilitating this accumulation remains unclear. Using in-vivo multimodal imaging, we show that the distribution of tau and reactive microglia in humans follows spatial patterns of connectivity variation, the so-called gradients of brain organization.

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Neuronal dysfunction and cognitive deterioration in Alzheimer's disease (AD) are likely caused by multiple pathophysiological factors. However, mechanistic evidence in humans remains scarce, requiring improved non-invasive techniques and integrative models. We introduce personalized AD computational models built on whole-brain Wilson-Cowan oscillators and incorporating resting-state functional MRI, amyloid-β (Aβ) and tau-PET from 132 individuals in the AD spectrum to evaluate the direct impact of toxic protein deposition on neuronal activity.

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Article Synopsis
  • - The study investigates the role of microglia in the brainstem related to Alzheimer's disease (AD) using TSPO PET imaging, focusing particularly on the inferior colliculi (IC) due to its potential link to auditory dysfunction.
  • - Results indicated that TSPO expression in the IC decreases with age and in AD patients, contrasting with increased TSPO expression in the cortex with aging and AD, suggesting different roles for microglia in these regions.
  • - The findings emphasize the need for further research on brainstem microglia, as their activation in the IC might serve a protective function, highlighting regional differences in the pathology of AD.
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Blood-based biomarkers for screening may guide tau positrion emissition tomography (PET) scan referrals to optimize prognostic evaluation in Alzheimer's disease. Plasma Aβ42/Aβ40, pTau181, pTau217, pTau231, NfL, and GFAP were measured along with tau-PET in memory clinic patients with subjective cognitive decline, mild cognitive impairment or dementia, in the Swedish BioFINDER-2 study (n = 548) and in the TRIAD study (n = 179). For each plasma biomarker, cutoffs were determined for 90%, 95%, or 97.

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The progression of PET-based Braak stages correlates with cognitive deterioration in aging and Alzheimer's disease. Here, we investigate the association between PET-based Braak stages and functional impairment and assess whether PET-based Braak staging predicts a longitudinal decline in the performance of activities of daily living. In this cohort study, we evaluated cognitively unimpaired individuals and individuals with mild cognitive impairment or Alzheimer's disease dementia.

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Background: Blood-based biomarkers of Alzheimer's disease (AD) have become increasingly important as scalable tools for diagnosis and determining clinical trial eligibility. P-tau217 is the most promising due to its excellent sensitivity and specificity for AD-related pathological changes.

Methods: We compared the performance of two commercially available plasma p-tau217 assays (ALZpath p-tau217 and Janssen p-tau217+) in 294 individuals cross-sectionally.

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Article Synopsis
  • Phosphorylated tau (p-tau) is a key blood biomarker for detecting Alzheimer disease (AD), with p-tau217 being particularly useful; however, access to p-tau217 tests has been limited, hindering research and clinical applications.
  • The study aimed to evaluate a new commercial immunoassay for plasma p-tau217, focusing on its ability to detect AD pathology and establish reference ranges for abnormal amyloid β (Aβ) across three different cohorts.
  • Involving 786 participants, the study found that plasma p-tau217 demonstrated high accuracy (AUC 0.92-0.96) in identifying elevated Aβ and tau pathology, suggesting its effectiveness as
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Article Synopsis
  • Antibody-based immunoassays effectively measure low levels of phosphorylated tau (p-tau) in cerebrospinal fluid (CSF), aiding Alzheimer’s disease (AD) diagnosis, and are compared to mass spectrometry for performance evaluation.
  • The study involved 567 participants and used both techniques to analyze p-tau concentrations, alongside clinical evaluations and PET scans for amyloid and tau.
  • Results indicate that while immunoassays show slightly superior diagnostic performance compared to mass spectrometry, the latter offers the advantage of assessing multiple biomarkers simultaneously, warranting further investigation.
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Post-mortem staging of Alzheimer's disease (AD) neurofibrillary pathology is commonly performed by immunohistochemistry using AT8 antibody for phosphorylated tau (p-tau) at positions 202/205. Thus, quantification of p-tau205 and p-tau202 in cerebrospinal fluid (CSF) should be more reflective of neurofibrillary tangles in AD than other p-tau epitopes. We developed two novel Simoa immunoassays for CSF p-tau205 and p-tau202 and measured these phosphorylations in three independent cohorts encompassing the AD continuum, non-AD cases and cognitively unimpaired participants: a discovery cohort (n = 47), an unselected clinical cohort (n = 212) and a research cohort well-characterized by fluid and imaging biomarkers (n = 262).

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Hippocampal atrophy is a well-known feature of age-related memory decline, and hippocampal subfields may contribute differently to this decline. In this cross-sectional study, we investigated the associations between hippocampal subfield volumes and performance in free recall and recognition memory tasks in both verbal and visual modalities in older adults without dementia. We collected MRIs from 97 (41 males) right-handed participants aged over 60.

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Importance: Neuropsychiatric symptoms are commonly encountered and are highly debilitating in patients with Alzheimer disease. Understanding their underpinnings has implications for identifying biomarkers and treatment for these symptoms.

Objective: To evaluate whether glial markers are associated with neuropsychiatric symptoms in individuals across the Alzheimer disease continuum.

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Introduction: Synaptic loss is closely associated with tau aggregation and microglia activation in later stages of Alzheimer's disease (AD). However, synaptic damage happens early in AD at the very early stages of tau accumulation. It remains unclear whether microglia activation independently causes synaptic cleavage before tau aggregation appears.

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Females are disproportionately affected by dementia due to Alzheimer's disease. Despite a similar amyloid-β (Aβ) load, a higher load of neurofibrillary tangles (NFTs) is seen in females than males. Previous literature has proposed that Aβ and phosphorylated-tau (p-tau) synergism accelerates tau tangle formation, yet the effect of biological sex in this process has been overlooked.

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