Network abnormalities and interneuron dysfunction in Alzheimer disease.
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ABSTRACT:
SUBMITTER: Palop JJ
PROVIDER: S-EPMC8162106 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Alzheimer's disease (AD) results in cognitive decline and altered network activity, but the mechanisms are unknown. We studied human amyloid precursor protein (hAPP) transgenic mice, which simulate key aspects of AD. Electroencephalographic recordings in hAPP mice revealed spontaneous epileptiform discharges, indicating network hypersynchrony, primarily during reduced gamma oscillatory activity. Because this oscillatory rhythm is generated by inhibitory parvalbumin (PV) cells, network dysfunction in hAPP mice might arise from impaired PV cells. Supporting this hypothesis, hAPP mice and AD patients had decreased levels of the interneuron-specific and PV cell-predominant voltage-gated sodium channel subunit Nav1.1. Restoring Nav1.1 levels in hAPP mice by Nav1.1-BAC expression increased inhibitory synaptic activity and gamma oscillations and reduced hypersynchrony, memory deficits, and premature mortality. We conclude that reduced Nav1.1 levels and PV cell dysfunction critically contribute to abnormalities in oscillatory rhythms, network synchrony, and memory in hAPP mice and possibly in AD.
| S-EPMC3375906 | biostudies-literature
Project description:ObjectiveTo examine the relationship between scalp EEG biomarkers of hyperexcitability in Alzheimer disease (AD) and to determine how these electric biomarkers relate to the clinical expression of seizures in AD.MethodsIn this cross-sectional study, we performed 24-hour ambulatory scalp EEGs on 43 cognitively normal elderly healthy controls (HC), 41 participants with early-stage AD with no history or risk factors for epilepsy (AD-NoEp), and 15 participants with early-stage AD with late-onset epilepsy related to AD (AD-Ep). Two epileptologists blinded to diagnosis visually reviewed all EEGs and annotated all potential epileptiform abnormalities. A panel of 9 epileptologists blinded to diagnosis was then surveyed to generate a consensus interpretation of epileptiform abnormalities in each EEG.ResultsEpileptiform abnormalities were seen in 53% of AD-Ep, 22% of AD-NoEp, and 4.7% of HC. Specific features of epileptiform discharges, including high frequency, robust morphology, right temporal location, and occurrence during wakefulness and REM, were associated with clinical seizures in AD. Multiple EEG biomarkers concordantly demonstrated a pattern of left temporal lobe hyperexcitability in early stages of AD, whereas clinical seizures in AD were often associated with bitemporal hyperexcitability. Frequent small sharp spikes were specifically associated with epileptiform EEGs and thus identified as a potential biomarker of hyperexcitability in AD.ConclusionEpileptiform abnormalities are common in AD but not all equivalent. Specific features of epileptiform discharges are associated with clinical seizures in AD. Given the difficulty recognizing clinical seizures in AD, these EEG features could provide guidance on which patients with AD are at high risk for clinical seizures.
| S-EPMC7713786 | biostudies-literature
Project description:Deficits in the generation and control of saccades have been described in clinically defined frontotemporal dementia (FTD) and Alzheimer disease (AD).To determine the saccade abnormalities associated with autopsy-defined cases of frontotemporal lobar degeneration (FTLD) and of AD, because clinical FTD syndromes can correspond to a number of different underlying neuropathologic FTD and non-FTD diagnoses.An infrared eye tracker was used to record visually guided saccades to 10° targets and antisaccades in subjects with autopsy-confirmed FTD and subjects with autopsy-confirmed AD, a mean (SE) of 35.6 (10.0) months prior to death, and age-matched normal controls. Twelve subjects with FTD had an FTLD-TAR DNA-binding protein 43 pathology, 15 had an FTLD-tau pathology, and 1 subject showed an FTLD-fused in sarcoma protein pathology. Receiver operating curve statistics were used to determine the diagnostic value of the oculomotor variables. Neuroanatomical correlates of oculomotor abnormalities were investigated using voxel-based morphometry.Memory and Aging Center, Department of Neurology, University of California, San Francisco.A total of 28 subjects with autopsy-confirmed FTD, 10 subjects with autopsy-confirmed AD, and 27 age-matched normal controls.All subjects with FTD or AD were impaired relative to normal controls on the antisaccade task. However, only FTLD-tau and AD cases displayed reflexive visually guided saccade abnormalities. The AD cases displayed prominent increases in horizontal saccade latency that differentiated them from the FTD cases. Impairments in velocity and gain were most severe in individuals with progressive supranuclear palsy but were also present in other tauopathies. By using vertical and horizontal saccade velocity and gain as our measures, we were able to differentiate patients with progressive supranuclear palsy from other patients. Vertical saccade velocity was strongly correlated with dorsal midbrain volume.Decreased visually guided saccade velocity and gain are suggestive of underlying tau pathology in FTD, with vertical saccade abnormalities most diagnostic of progressive supranuclear palsy.
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Project description:The mechanisms by which mutations in the presenilins (PSEN) or the amyloid precursor protein (APP) genes cause familial Alzheimer disease (FAD) are controversial. FAD mutations increase the release of amyloid ? (A?)42 relative to A?40 by an unknown, possibly gain-of-toxic-function, mechanism. However, many PSEN mutations paradoxically impair ?-secretase and 'loss-of-function' mechanisms have also been postulated. Here, we use kinetic studies to demonstrate that FAD mutations affect A? generation via three different mechanisms, resulting in qualitative changes in the A? profiles, which are not limited to A?42. Loss of ?-cleavage function is not generally observed among FAD mutants. On the other hand, ?-secretase inhibitors used in the clinic appear to block the initial ?-cleavage step, but unexpectedly affect more selectively Notch than APP processing, while modulators act as activators of the carboxypeptidase-like (?) activity. Overall, we provide a coherent explanation for the effect of different FAD mutations, demonstrating the importance of qualitative rather than quantitative changes in the A? products, and suggest fundamental improvements for current drug development efforts.
| S-EPMC3364747 | biostudies-literature
Project description:Research in amyotrophic lateral sclerosis (ALS) suggests that executive dysfunction, a prevalent cognitive feature of the disease, is associated with abnormal structural connectivity and white matter integrity. In this exploratory study, we investigated the white matter constructs of executive dysfunction, and attempted to detect structural abnormalities specific to cognitively impaired ALS patients. Eighteen ALS patients and 22 age and education matched healthy controls underwent magnetic resonance imaging on a 4.7 Tesla scanner and completed neuropsychometric testing. ALS patients were categorized into ALS cognitively impaired (ALSci, n = 9) and ALS cognitively competent (ALScc, n = 5) groups. Tract-based spatial statistics and connectomics were used to compare white matter integrity and structural connectivity of ALSci and ALScc patients. Executive function performance was correlated with white matter FA and network metrics within the ALS group. Executive function performance in the ALS group correlated with global and local network properties, as well as FA, in regions throughout the brain, with a high predilection for the frontal lobe. ALSci patients displayed altered local connectivity and structural integrity in these same frontal regions that correlated with executive dysfunction. Our results suggest that executive dysfunction in ALS is related to frontal network disconnectivity, which potentially mediates domain-specific, or generalized cognitive impairment, depending on the degree of global network disruption. Furthermore, reported co-localization of decreased network connectivity and diminished white matter integrity suggests white matter pathology underlies this topological disruption. We conclude that executive dysfunction in ALSci is associated with frontal and global network disconnectivity, underlined by diminished white matter integrity. Hum Brain Mapp 38:1249-1268, 2017. © 2016 Wiley Periodicals, Inc.
| S-EPMC6866969 | biostudies-literature
Project description:Cerebrovascular dysfunction is a hallmark feature of Alzheimer's disease (AD). One of the greatest risk factor for AD is the apolipoprotein E4 (E4) allele. APOE4 genotype has been shown to negatively impact on perivascular amyloid clearance, however, its direct influence along with the other APOE variants (APOE2 and APOE3) on the molecular integrity of the cerebrovasculature has not been largely explored. To address this, we employed a 10-plex tandem isobaric mass tag approach in combination with an ultra-high pressure liquid chromatography MS/MS (Q-Exactive) method, to interrogate unbiased proteomic changes in cerebrovessels from AD and healthy control brains on different APOE genotype backgrounds. We first interrogated changes between healthy control homozygote E2/E2, E3/E3 and E4/E4 cases to identify underlying genotype specific effects on cerebrovessels. EIF2 signaling, regulation of eIF4 and 70S6K signaling and mTOR signaling were the top significantly altered pathways in E4/E4 compared to E3/E3 cases. EIF2, nitric oxide and sirtuin signaling pathways were the top significantly altered pathways in E4/E4 compared to E2/E2 cases. We used a Two-way ANOVA analysis to identify AD-dependent changes and their interactions with APOE genotype. The highest number of significantly regulated proteins from this interaction was observed in E3/E4 (192) and E4/E4 (189) cases. As above, EIF2, mTOR signaling and eIF4 and 70S6K signaling were the top three significantly altered pathways in E4 allele carriers (i.e. E3/E4 and E4/E4 genotypes). Of all the cerebrovascular cell specific markers identified in our proteomic analyses, endothelial cell, astrocyte, and smooth muscle cell specific protein markers were significantly altered in E4/E4 cases, while endothelial cells and astrocyte specific protein markers were altered in E3/E4 cases. These proteomic changes provide novel insights to explain the longstanding link between APOE4 and cerebrovascular dysfunction. The early and converging APOE4 dependent changes we identified could provide novel targets in the cerebrovasculature for developing disease modifying strategies to mitigate the effects of APOE4 genotype on increasing the risk for, and the path towards AD pathogenesis.
2021-03-23 | PXD023340 | Pride
Project description:Our study aimed to analyse the olfactory dysfunction (OD) evaluations between self-report, the Hyposmia Rating Scale (HRS) and the Sniffin' Sticks test, and the relationship between OD and clinical features of AD. Sixty patients with AD dementia, 37 patients with mild cognitive impairment (MCI) due to AD and 30 healthy controls were consecutively recruited. Olfactory function was evaluated by self-report, HRS and Sniffin' Sticks test. Patients were divided into AD with OD (AD-OD) and AD with no OD (AD-NOD) groups based on the results of the Sniffin' Sticks test. Cognitive symptoms and neuropsychiatric symptoms were assessed by corresponding scales, and activities of daily living (ADL) were assessed by the ADL scale. In the control, MCI due to AD and AD dementia groups, the frequency of OD was 10.0%, 13.5% and 18.3%, respectively, by self-report; 6.7%, 24.3% and 48.3%, respectively, by HRS; and 3.3%, 13.5% and 65.0%, respectively, by the Sniffin' Sticks test. Compared to the results of the Sniffin' Sticks test, the diagnostic coincidence rates of OD by HRS in patients with MCI due to AD and AD dementia were 89.2% and 66.7%, respectively. Compared to the AD-NOD group, the scores of global cognition and memory, visuospatial ability and attention were all decreased (P<0.05), the apathy score was increased (P<0.05), and the ADL score was elevated (P<0.01). The frequency and accuracy of OD by self-report is relatively low. HRS can be used for screening olfaction in patients with MCI due to AD. The Sniffin' Sticks test can be used for validating OD in AD patients. AD-OD patients have severe impairments in global cognition and multiple cognitive domains of memory, visuospatial ability and attention, as well as neuropsychiatric symptoms of apathy, and thus have seriously compromised ADL.
| S-EPMC6284764 | biostudies-literature
Project description:ObjectiveTo measure CSF levels of biomarkers reflecting microglia and astrocytes activation, neuroinflammation, and cerebrovascular changes and study their associations with the core biomarkers of Alzheimer disease (AD) pathology (β-amyloid [Aβ] and tau), structural imaging correlates, and clinical disease progression over time.MethodsThe study included cognitively unimpaired elderly (n = 508), patients with mild cognitive impairment (MCI, n = 256), and patients with AD dementia (n = 57) from the longitudinal Swedish BioFINDER cohort. CSF samples were analyzed for YKL-40, interleukin (IL)-6, IL-7, IL-8, IL-15, IP-10, monocyte chemoattractant protein 1, intercellular adhesion molecule 1 (ICAM-1), vascular adhesion molecule 1 (VCAM-1), placental growth factor, and fms-related tyrosine kinase 1 (Flt-1). MRI data were available from 677 study participants. Longitudinal clinical assessments were conducted in control individuals and patients with MCI (mean follow-up 3 years, range 1-6 years).ResultsCSF levels of YKL-40, ICAM-1, VCAM-1, IL-15, and Flt-1 were increased during the preclinical, prodromal, and dementia stages of AD. High levels of these biomarkers were associated with increased CSF levels of total tau, with the associations, especially for YKL-40, being stronger in Aβ-positive individuals. The results were similar for associations between phosphorylated tau and YKL-40, ICAM-1, and VCAM-1. High levels of the biomarkers were also associated with cortical thinning (primarily in the precuneus and superior parietal regions) and with subsequent cognitive deterioration in patients without dementia as measured with Mini-Mental State Examination (YKL-40) and Clinical Dementia Rating Sum of Boxes (YKL-40, ICAM-1, VCAM-1 and IL-15). Finally, higher levels of CSF YKL-40, ICAM-1, and Flt-1 increased risk of development of AD dementia in patients without dementia.ConclusionsNeuroinflammation and cerebrovascular dysfunction are early events occurring already at presymptomatic stages of AD and contribute to disease progression.
| S-EPMC6133624 | biostudies-literature
Project description:To explore roles for ephrin-B/EphB signaling in cortical interneurons, we previously generated ephrin-B (Efnb1/b2/b3) conditional triple mutant (TMlz ) mice using a Dlx1/2.Cre inhibitory neuron driver and green fluorescent protein (GFP) reporters for the two main inhibitory interneuron groups distinguished by expression of either glutamic acid decarboxylase 1 (GAD1; GAD67-GFP) or 2 (GAD2; GAD65-GFP). This work showed a general involvement of ephrin-B in migration and population of interneurons into the embryonic neocortex. We now determined whether specific interneurons are selectively affected in the adult brains of TMlz .Cre mice by immunostaining with antibodies that identify the different subtypes. The results indicate that GAD67-GFP-expressing interneurons that also express parvalbumin (PV), calretinin (CR) and, to a lesser extent, somatostatin (SST) and Reelin (Rln) were significantly reduced in the cortex and hippocampal CA1 region in TMlz .Cre mutant mice. Neuropeptide Y (NPY) interneurons that also express GAD67-GFP were reduced in the hippocampal CA1 region, but much less so in the cortex, although these cells exhibited abnormal cortical layering. In GAD65-GFP-expressing interneurons, CR subtypes were reduced in both cortex and hippocampal CA1 region, whereas Rln interneurons were reduced exclusively in hippocampus, and the numbers of NPY and vasoactive intestinal polypeptide (VIP) subtypes appeared normal. PV and CR subtype interneurons in TMlz .Cre mice also exhibited reductions in their perisomatic area, suggesting abnormalities in dendritic/axonal complexity. Altogether, our data indicate that ephrin-B expression within forebrain interneurons is required in specific subtypes for their normal population, cortical layering and elaboration of cell processes.
| S-EPMC6105433 | biostudies-literature
Project description:Alterations in inhibitory (GABA) neurons, including deficiencies in the GABA synthesizing enzyme GAD67, in the prefrontal cortex in schizophrenia are pronounced in the subpopulations of neurons that contain the calcium-binding protein parvalbumin or the neuropeptide somatostatin. The presence of similar illness-related deficits in the transcription factor Lhx6, which regulates prenatal development of parvalbumin and somatostatin neurons, suggests that cortical GABA neuron dysfunction may be related to disturbances in utero. Since the chemokine receptors CXCR4 and CXCR7 guide the migration of cortical parvalbumin and somatostatin neurons from their birthplace in the medial ganglionic eminence to their final destination in the neocortex, we sought to determine whether altered CXCR4 and/or CXCR7 mRNA levels were associated with disturbances in GABA-related markers in schizophrenia. Quantitative PCR was used to quantify CXCR4 and CXCR7 mRNA levels in the prefrontal cortex of 62 schizophrenia and 62 healthy comparison subjects that were previously characterized for markers of parvalbumin and somatostatin neurons and in antipsychotic-exposed monkeys. We found elevated mRNA levels for CXCR7 (+29%; p<.0001) and CXCR4 (+14%, p=.052) in schizophrenia subjects but not in antipsychotic-exposed monkeys. CXCR7 mRNA levels were inversely correlated with mRNA levels for GAD67, parvalbumin, somatostatin, and Lhx6 in schizophrenia but not in healthy subjects. These findings suggest that higher mRNA levels for CXCR7, and possibly CXCR4, may represent a compensatory mechanism to sustain the migration and correct positioning of cortical parvalbumin and somatostatin neurons in the face of other insults that disrupt the prenatal development of cortical GABA neurons in schizophrenia.
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