Alzheimer's Disease Hippocampus Research Articles

Abundance of P-Glycoprotein and Other Drug Transporters at the Human Blood-Brain Barrier in Alzheimer's Disease: A Quantitative Targeted Proteomic Study.

The human blood-brain barrier (BBB) transporter P-gp can efflux amyloid-β (Aβ) out of the central nervous system (CNS). Aβ is thought to be the causative agent for Alzheimer's disease (AD). Using positron emission tomography imaging, we have shown that BBB P-gp activity is reduced in AD, as quantified by the in vivo brain distribution of the P-gp probe [11 C]-verapamil. Therefore, the aim of this study was to determine whether this reduced BBB P-gp activity in AD was due to decreased P-gp abundance at the BBB. Using targeted proteomics, we quantified the abundance of P-gp and other drug transporters in gray matter brain microvessels isolated from 43 subjects with AD and 38 age-matched controls (AMCs) from regions affected by AD (hippocampus and the parietal lobe of the brain cortex) and not affected by AD (cerebellum). First, P-gp abundance was decreased in the BBB of the hippocampus vs. the cerebellum in both subjects with AD and AMCs, and therefore was not AD-related. In addition, gray matter BBB abundance of P-gp (and of other transporters) in the hippocampus and the parietal lobe was not different between AD and AMC. The gray matter BBB abundance of all drug transporters decreased with age, likely due to age-dependent decrease in the density of brain microvessels. Collectively, the observed reduced in vivo cerebral BBB P-gp activity in AD cannot be explained by reduced abundance of P-gp at the BBB. Nevertheless, the drug transporter abundance at the human gray matter BBB data provided here can be used to predict brain distribution of drugs targeted to treat CNS diseases, including AD.

DNA Double-Strand Break Accumulation in Alzheimer's Disease: Evidence from Experimental Models and Postmortem Human Brains.

Alzheimer's disease (AD) is a progressive neurodegenerative disease that accounts for a majority of dementia cases. AD is characterized by progressive neuronal death associated with neuropathological lesions consisting of neurofibrillary tangles and senile plaques. While the pathogenesis of AD has been widely investigated, significant gaps in our knowledge remain about the cellular and molecular mechanisms promoting AD. Recent studies have highlighted the role of DNA damage, particularly DNA double-strand breaks (DSBs), in the progression of neuronal loss in a broad spectrum of neurodegenerative diseases. In the present study, we tested the hypothesis that accumulation of DNA DSB plays an important role in AD pathogenesis. To test our hypothesis, we examined DNA DSB expression and DNA repair function in the hippocampus of human AD and non-AD brains by immunohistochemistry, ELISA, and RT-qPCR. We observed increased DNA DSB accumulation and reduced DNA repair function in the hippocampus of AD brains compared to the non-AD control brains. Next, we found significantly increased levels of DNA DSB and altered levels of DNA repair proteins in the hippocampus of 5xFAD mice compared to non-transgenic mice. Interestingly, increased accumulation of DNA DSBs and altered DNA repair proteins were also observed in cellular models of AD. These findings provided compelling evidence that AD is associated with accumulation of DNA DSB and/or alteration in DSB repair proteins which may influence an important early part of the pathway toward neural damage and memory loss in AD.

Electroacupuncture at GV24 and bilateral GB13 improves cognitive ability via influences the levels of Aβ, p-tau (s396) and p-tau (s404) in the hippocampus of Alzheimer's disease model rats.

Acupuncture is widely used to treat various neurodegenerative diseases and can effectively improve cognitive and memory states in Alzheimer's disease. However, its mechanism is unclear. We speculated that the effect of acupuncture on cognitive function may be associated with reductions in the levels of Aβ and phosphorylated tau in the brain. In this experiment, 60 male Sprague-Dawley rats were randomly divided into control, model, electroacupuncture and nonacupoint groups. We perform electroacupuncture at Shenting (GV24) and bilateral Benshen (GB13) acupoints once a day for 4 weeks in electroacupuncture group (with 1 day of rest after every 6 days of treatment). The electroacupuncture group showed a better performance in cognitive-related behavior tests and significantly lowers the levels of Aβ, p-tau (s396) and p-tau (s404) in the hippocampus. These results may suggest that electroacupuncture at the GV24 and bilateral GB13 acupoints might improve cognitive functions in Alzheimer's disease by decreasing the levels of Aβ, p-tau (s396) and p-tau (s404) in the brain as these proteins are the main causes of neurological damage and cognitive dysfunction during the pathogenesis underlying Alzheimer's disease.

Alogliptin reversed hippocampal insulin resistance in an amyloid-beta fibrils induced animal model of Alzheimer's disease

The complications of Alzheimer's disease (AD) have made the development of its treatment a challenging task. Several studies have indicated the disruption of insulin receptor substrate-1 (IRS-1) signaling during the development and progression of AD. The role of a dipeptidyl peptidase-4 (DPP-4) inhibitor on hippocampal IRS-1 signaling has not been investigated before. In this study, we evaluated the efficacy of alogliptin (DPP-4 inhibitor) on hippocampal insulin resistance and associated AD complications. In the present study, amyloid-β (1–42) fibrils were produced and administered intrahippocampally for inducing AD in Wistar rats. After 7 days of surgery, rats were treated with 10 and 20 mg/kg of alogliptin for 28 days. Morris water maze (MWM) test was performed in the last week of our experimental study. Post 24 h of final treatment, rats were euthanized and hippocampi were separated for biochemical and histopathological investigations. In-silico analysis revealed that alogliptin has a good binding affinity with Aβ and beta-secretase-1 (BACE-1). Alogliptin significantly restored cognitive functions in Aβ (1–42) fibrils injected rats during the MWM test. Alogliptin also significantly attenuated insulin level, IRS-1pS307 expression, Aβ (1–42) level, GSK-3β activity, TNF-α level and oxidative stress in the hippocampus. The histopathological analysis supported alogliptin mediated neuroprotective and anti-amyloidogenic effect. Immunohistochemical analysis also revealed a reduction in IRS-1pS307 expression after alogliptin treatment. The in-silico, behavioral, biochemical and histopathological analysis supports the protective effect of alogliptin against hippocampal insulin resistance and AD.

Embryonic proteoglycans regulate monoamines in the rat frontal cortex and hippocampus in Alzheimer's disease-like pathology

Using the rat Alzheimer's disease (AD)-like model we have analyzed the hippocampal short-term potentiation, levels of monoamines, and morphological changes in the hippocampal and cortical neurons after the administration of proteoglycans of embryonic origin (PEG). Results showed that the levels of monoamines and especially norepinephrine in the target AD brain structures were found elevated, except serotonin, which was unaffected in the hippocampus, but decreased in the frontal cortex. These changes were accompanied by the substantial structural damage of cortical and hippocampal neurons. PEG was able to reverse most of these changes. In addition, PEG administration had regime-dependent effects on a short-term potentiation pattern of hippocampal neurons. The elevated levels of key elements of brain monoaminergic system in the model of AD support the hypothesis of the important role of monoamines in the excessive synaptic excitation resulting in cognitive dysfunction in AD brain. The neuroprotective effect of PEG, as manifested by the recovery of the monoaminergic system, suggests this bioactive substance as a perspective therapeutic agent for the treatment of AD.

Functional Connectivity Alterations of the Temporal Lobe and Hippocampus in Semantic Dementia and Alzheimer's Disease.

Background:Semantic memory impairments in semantic dementia are attributed to atrophy and functional disruption of the anterior temporal lobes. In contrast, the posterior medial temporal neurodegeneration found in Alzheimer’s disease is associated with episodic memory disturbance. The two dementia subtypes share hippocampal deterioration, despite a relatively spared episodic memory in semantic dementia.Objective:To unravel mutual and divergent functional alterations in Alzheimer’s disease and semantic dementia, we assessed functional connectivity between temporal lobe regions in Alzheimer’s disease (n = 16), semantic dementia (n = 23), and healthy controls (n = 17).Methods:In an exploratory study, we used a functional parcellation of the temporal cortex to extract time series from 66 regions for correlation analysis.Results:Apart from differing connections between Alzheimer’s disease and semantic dementia that yielded reduced functional connectivity, we identified a common pathway between the right anterior temporal lobe and the right orbitofrontal cortex in both dementia subtypes. This disconnectivity might be related to social knowledge deficits as part of semantic memory decline. However, such interpretations are preferably made in a holistic context of disease-specific semantic impairments and functional connectivity changes.Conclusion:Despite a major limitation owed to unbalanced databases between study groups, this study provides a preliminary picture of the brain’s functional disconnectivity in Alzheimer’s disease and semantic dementia. Future studies are needed to replicate findings of a common pathway with consistent diagnostic criteria and neuropsychological evaluation, balanced designs, and matched data MRI acquisition procedures.

The unfolded protein response is activated in the olfactory system in Alzheimer\u2019s disease

Olfactory dysfunction is an early and prevalent symptom of Alzheimer’s disease (AD) and the olfactory bulb is a nexus of beta-amyloid plaque and tau neurofibrillary tangle (NFT) pathology during early AD progression. To mitigate the accumulation of misfolded proteins, an endoplasmic reticulum stress response called the unfolded protein response (UPR) occurs in the AD hippocampus. However, chronic UPR activation can lead to apoptosis and the upregulation of beta-amyloid and tau production. Therefore, UPR activation in the olfactory system could be one of the first changes in AD. In this study, we investigated whether two proteins that signal UPR activation are expressed in the olfactory system of AD cases with low or high amounts of aggregate pathology. We used immunohistochemistry to label two markers of UPR activation (p-PERK and p-eIF2α) concomitantly with neuronal markers (NeuN and PGP9.5) and pathology markers (beta-amyloid and tau) in the olfactory bulb, piriform cortex, entorhinal cortex and the CA1 region of the hippocampus in AD and normal cases. We show that UPR activation, as indicated by p-PERK and p-eIF2α expression, is significantly increased throughout the olfactory system in AD cases with low (Braak stage III-IV) and high-level (Braak stage V-VI) pathology. We further show that UPR activation occurs in the mitral cells and in the anterior olfactory nucleus of the olfactory bulb where tau and amyloid pathology is abundant. However, UPR activation is not present in neurons when they contain NFTs and only rarely occurs in neurons containing diffuse tau aggregates. We conclude that UPR activation is prevalent in all regions of the olfactory system and support previous findings suggesting that UPR activation likely precedes NFT formation. Our data indicate that chronic UPR activation in the olfactory system might contribute to the olfactory dysfunction that occurs early in the pathogenesis of AD.

HGF Mediates Clinical‐Grade Human Umbilical Cord‐Derived Mesenchymal Stem Cells Improved Functional Recovery in a Senescence‐Accelerated Mouse Model of Alzheimer's Disease

Stem cells have emerged as a potential therapy for a range of neural insults, but their application in Alzheimer's disease (AD) is still limited and the mechanisms underlying the cognitive benefits of stem cells remain to be elucidated. Here, the effects of clinical‐grade human umbilical cord‐derived mesenchymal stem cells (hUC‐MSCs) on the recovery of cognitive ability in SAMP8 mice, a senescence‐accelerated mouse model of AD is explored. A functional assay identifies that the core functional factor hepatocyte growth factor (HGF) secreted from hUC‐MSCs plays critical roles in hUC‐MSC‐modulated recovery of damaged neural cells by down‐regulating hyperphosphorylated tau, reversing spine loss, and promoting synaptic plasticity in an AD cell model. Mechanistically, structural and functional recovery, as well as cognitive enhancements elicited by exposure to hUC‐MSCs, are at least partially mediated by HGF in the AD hippocampus through the activation of the cMet‐AKT‐GSK3β signaling pathway. Taken together, these data strongly implicate HGF in mediating hUC‐MSC‐induced improvements in functional recovery in AD models.

Learning the spatiotemporal variability in longitudinal shape data sets

In this paper, we propose a generative statistical model to learn the spatiotemporal variability in longitudinal shape data sets, which contain repeated observations of a set of objects or individuals over time. From all the short-term sequences of individual data, the method estimates a long-term normative scenario of shape changes and a tubular coordinate system around this trajectory. Each individual data sequence is therefore (i) mapped onto a specific portion of the trajectory accounting for differences in pace of progression across individuals, and (ii) shifted in the shape space to account for intrinsic shape differences across individuals that are independent of the progression of the observed process. The parameters of the model are estimated using a stochastic approximation of the expectation–maximization algorithm. The proposed approach is validated on a simulated data set, illustrated on the analysis of facial expression in video sequences, and applied to the modeling of the progressive atrophy of the hippocampus in Alzheimer’s disease patients. These experiments show that one can use the method to reconstruct data at the precision of the noise, to highlight significant factors that may modulate the progression, and to simulate entirely synthetic longitudinal data sets reproducing the variability of the observed process.

Amyloid-beta1-42 induced glutamatergic receptor and transporter expression changes in the mouse hippocampus.

Alzheimer's disease (AD) is the leading type of dementia worldwide. With an increasing burden of an aging population coupled with the lack of any foreseeable cure, AD warrants the current intense research effort on the toxic effects of an increased concentration of beta-amyloid (Aβ) in the brain. Glutamate is the main excitatory brain neurotransmitter and it plays an essential role in the function and health of neurons and neuronal excitability.While previous studies have shownalterations in expression of glutamatergic signaling components in AD, the underlying mechanisms of these changes are not well understood. This is the first comprehensive anatomical study to characterize the subregion- and cell layer-specific long-term effect of Aβ1-42 on the expression of specific glutamate receptors and transporters in the mouse hippocampus, using immunohistochemistry with confocal microscopy. Outcomes are examined 30days after Aβ1-42 stereotactic injection in aged male C57BL/6 mice. We report significant decreases in density of the glutamate receptor subunit GluA1 and the vesicular glutamate transporter (VGluT) 1 in the conus ammonis 1 region of the hippocampus in the Aβ1-42 injected mice compared with artificial cerebrospinal fluid injected and naïve controls, notably in the stratum oriens and stratum radiatum. GluA1 subunit density also decreased within the dentate gyrus dorsal stratum moleculare in Aβ1-42 injected mice compared with artificial cerebrospinal fluid injected controls. These changes are consistent with findings previously reported in the human AD hippocampus. By contrast, glutamate receptor subunits GluA2, GluN1, GluN2A, and VGluT2 showed no changes in expression. These findings indicate that Aβ1-42 induces brain region and layer specific expression changes of the glutamatergic receptors and transporters, suggesting complex and spatial vulnerability of this pathway during development of AD neuropathology. Read the Editorial Highlight for this article on page 7. Cover Image for this issue: https://doi.org/10.1111/jnc.14763.

Cyclase-associated protein 2 dimerization regulates cofilin in synaptic plasticity and Alzheimer's disease.

Regulation of actin cytoskeleton dynamics in dendritic spines is crucial for learning and memory formation. Hence, defects in the actin cytoskeleton pathways are a biological trait of several brain diseases, including Alzheimer's disease. Here, we describe a novel synaptic mechanism governed by the cyclase-associated protein 2, which is required for structural plasticity phenomena and completely disrupted in Alzheimer's disease. We report that the formation of cyclase-associated protein 2 dimers through its Cys32 is important for cyclase-associated protein 2 binding to cofilin and for actin turnover. The Cys32-dependent cyclase-associated protein 2 homodimerization and association to cofilin are triggered by long-term potentiation and are required for long-term potentiation-induced cofilin translocation into spines, spine remodelling and the potentiation of synaptic transmission. This mechanism is specifically affected in the hippocampus, but not in the superior frontal gyrus, of both Alzheimer's disease patients and APP/PS1 mice, where cyclase-associated protein 2 is down-regulated and cyclase-associated protein 2 dimer synaptic levels are reduced. Notably, cyclase-associated protein 2 levels in the cerebrospinal fluid are significantly increased in Alzheimer's disease patients but not in subjects affected by frontotemporal dementia. In Alzheimer's disease hippocampi, cofilin association to cyclase-associated protein 2 dimer/monomer is altered and cofilin is aberrantly localized in spines. Taken together, these results provide novel insights into structural plasticity mechanisms that are defective in Alzheimer's disease.

Knockdown of long non-coding RNA TUG1 depresses apoptosis of hippocampal neurons in Alzheimer's disease by elevating microRNA-15a and repressing ROCK1 expression.

Many studies have already suggested the role of long non-coding RNAs (lncRNAs) in Alzheimer's disease (AD), but the functions of lncRNA Taurine Upregulated Gene 1 (TUG1) in AD have been scarcely discussed. This study aims to verify how TUG1 affects hippocampal neurons in AD through modulation of microRNA-15a (miR-15a)/Rho-associated protein kinase 1 (ROCK1). AD mice was modeled through injection of β-amyloid 25-35 (Aβ25-35) into the lateral ventricle. After modeling, the mice were injected with altered TUG1 and/or miR-15a agomir lentiviruses. The spatial learning ability and memory ability of mice were detected through Morris water maze test. Hippocampal neuronal apoptosis and oxidative stress indicators in AD mice were then detected. The hippocampal neuron AD model was induced by Aβ25-35. Next, the neurons were, respectively, transfected with altered TUG1 vector and/or miR-15a mimics to determine the proliferation inhibition and apoptosis of hippocampal neurons. The interactions between TUG1 and miR-15a, and between miR-15a and ROCK1 were assessed using bioinformatic prediction, dual luciferase reporter gene assay and RNA-pull-down assay. In the animal models, Aβ25-35-induced mice exhibited decreased spatial learning and memory ability, obvious pathological injury, promoted hippocampal neuronal apoptosis and decreased antioxidant ability. TUG1 silencing and miR-15a elevation improved spatial learning ability and memory ability, ameliorated pathological injury, depressed neuronal apoptosis, and strengthened antioxidant ability of hippocampal neurons in AD mice. In cellular models, Aβ25-35-treated hippocampal neurons presented inhibited neuronal viability and promoted neuronal apoptosis. TUG1 silencing and miR-15a elevation increased viability and limited apoptosis of Aβ25-35-treated hippocampal neurons. TUG1 specifically bound to miR-15a, and miR-15a targeted ROCK1. Collectively, this study reveals that TUG1 knockdown restricts apoptosis of hippocampal neurons in AD by elevating miR-15a and suppressing ROCK1 expression, and provides a new therapeutic target for AD treatment.

Aberrant Hippocampal Functional Connectivity Is Associated with Fornix White Matter Integrity in Alzheimer's Disease and Mild Cognitive Impairment.

Alzheimer's disease (AD) is the most common cause of dementia in older individuals, and amnestic mild cognitive impairment (aMCI) is currently considered the prodromal stage of AD. The hippocampus and fornix interact functionally and structurally, with the fornix being the major efferent white matter tract from the hippocampus. The main aim of this study was to examine the impairments present in subjects with AD or aMCI and the relationship of these impairments with the microstructure of the fornix and the functional connectivity (FC) and gray matter volume of the hippocampus. Forty-four AD, 34 aMCI, and 41 age- and gender-matched normal controls (NCs) underwent neuropsychological assessments and multimode MRI. We chose the bilateral hippocampi as the region of interest in which gray matter alterations and FC with the whole brain were assessed and the fornix body as the region of interest in which the microstructural integrity of the white matter was observed. We also evaluated the relationship among gray matter alterations, the abnormal FC of the hippocampus and the integrity of the fornix in AD/aMCIResults:Compared to the NC group, the AD and aMCI groups demonstrated decreased gray matter volume, reduced FC between the bilateral hippocampi and several brain regions in the default mode network and control network, and damaged integrity of the fornix body (decreased fractional anisotropy and increased diffusivity). We also found that left hippocampal FC with some regions, the integrity of the fornix body, and cognition ability were significantly correlated. Therefore, our findings suggest that damage to white matter integrity may partially explain the reduced resting-state FC of the hippocampus in AD and aMCI. AD and aMCI are diseases of disconnectivity including not only functional but also structural disconnectivity. Damage to white matter integrity may partially explain the reduced resting-state FC in AD and aMCI. These findings have significant implications for diagnostics and modeling and provide insights for understanding the disconnection syndrome in AD.

Lack of Helios During Neural Development Induces Adult Schizophrenia-Like Behaviors Associated With Aberrant Levels of the TRIF-Recruiter Protein WDFY1.

The role of the WDFY1 protein has been studied as a TLR3/4 scaffold/recruiting protein in the immune system and in different oncogenic conditions. However, its function in brain remains poorly understood. We have found that in mice devoid of Helios (He–/– mice), a transcription factor specifically expressed during the development of the immune cells and the central nervous system, there is a permanent and sustained increase of Wdfy1 gene expression in the striatum and hippocampus. Interestingly, we observed that WDFY1 protein levels were also increased in the hippocampus and dorsolateral prefrontal cortex of schizophrenic patients, but not in the hippocampus of Alzheimer’s disease patients with an associated psychotic disorder. Accordingly, young He–/– mice displayed several schizophrenic-like behaviors related to dysfunctions in the striatum and hippocampus. These changes were associated with an increase in spine density in medium spiny neurons (MSNs) and with a decrease in the number and size of PSD-95-positive clusters in the stratum radiatum of the CA1. Moreover, these alterations in structural synaptic plasticity were associated with a strong reduction of neuronal NF-κB in the pyramidal layer of the CA1 in He–/– mice. Altogether, our data indicate that alterations involving the molecular axis Helios-WDFY1 in neurons during the development of core brain regions could be relevant for the pathophysiology of neuropsychiatric disorders such as schizophrenia.

Neuroligin-1 is altered in the hippocampus of Alzheimer\u2019s disease patients and mouse models, and modulates the toxicity of amyloid-beta oligomers

Synapse loss occurs early and correlates with cognitive decline in Alzheimer’s disease (AD). Synaptotoxicity is driven, at least in part, by amyloid-beta oligomers (Aβo), but the exact synaptic components targeted by Aβo remain to be identified. We here tested the hypotheses that the post-synaptic protein Neuroligin-1 (NLGN1) is affected early in the process of neurodegeneration in the hippocampus, and specifically by Aβo, and that it can modulate Aβo toxicity. We found that hippocampal NLGN1 was decreased in patients with AD in comparison to patients with mild cognitive impairment and control subjects. Female 3xTg-AD mice also showed a decreased NLGN1 level in the hippocampus at an early age (i.e., 4 months). We observed that chronic hippocampal Aβo injections initially increased the expression of one specific Nlgn1 transcript, which was followed by a clear decrease. Lastly, the absence of NLGN1 decreased neuronal counts in the dentate gyrus, which was not the case in wild-type animals, and worsens impairment in spatial learning following chronic hippocampal Aβo injections. Our findings support that NLGN1 is impacted early during neurodegenerative processes, and that Aβo contributes to this effect. Moreover, our results suggest that the presence of NLGN1 favors the cognitive prognosis during Aβo-driven neurodegeneration.

Reduced uptake of [11C]‐ABP688, a PET tracer for metabolic glutamate receptor 5 in hippocampus and amygdala in Alzheimer’s dementia

IntroductionMetabotropic glutamate receptors play a critical role in the pathogenesis of Alzheimer's disease due to their involvement in processes of memory formation, neuroplasticity, and synaptotoxity. The objective of the current study was to study mGluR5 availability measured by [11C]‐ABP688 (ABP) in patients with clinically diagnosed Alzheimer's dementia (AD).MethodsA bolus‐infusion protocol of [11C]‐ABP688 was applied in 9 subjects with AD and 10 cognitively healthy controls (Controls) to derive distribution volume estimates of mGluR5. Furthermore, we also estimated cerebral perfusion by averaging early frame signal of initial ABP bolus injection.ResultsSubjects with Alzheimer's dementia (mean age: 77.3/SD 5.7) were older than controls (mean age: 68.5/SD: 9.6) and scored lower on the MMSE (22.1/SD2.7 vs. 29.0/SD0.8). There were no overall differences in ABP signal. However, distribution volume ratio (DVR) for ABP was reduced in the bilateral hippocampus (AD: 1.34/SD: 0.40 vs. Control: 1.84/SD:0.31, p = .007) and the bilateral amygdala (AD:1.86/SD:0.26 vs. Control:2.33/SD:0.37 p = .006) in AD patients compared to controls.Estimate of cerebral blood flow was reduced in the bilateral hippocampus in AD (AD:0.75/SD:0.10 vs. Control:0.86/SD:0.09 p = .02).ConclusionOur findings demonstrate reduced mGluR5 binding in the hippocampus and amygdala in Alzheimer's dementia. Whether this is due to synaptic loss and/or consecutive reduction of potential binding sites or reflects disease inherent mechanisms remains to be elucidated in future studies.

Early epigenetic changes of Alzheimer’s disease in the human hippocampus

ABSTRACT The discovery of new biomarkers would be very valuable to improve the detection of early Alzheimer’s disease (AD). DNA methylation marks may serve as epigenetic biomarkers of early AD. Here we identified epigenetic marks that are present in the human hippocampus from the earliest stages of AD. A previous methylome dataset of the human AD hippocampus was used to select a set of eight differentially methylated positions (DMPs) since early AD stages. Next, bisulphite pyrosequencing was performed in an expanded homogeneous cohort of 18 pure controls and 35 hippocampal samples with neuropathological changes of pure AD. Correlation between DNA methylation levels in DMPs and phospho-tau protein burden assessed by immunohistochemistry in the hippocampus was also determined. We found four DMPs showing higher levels of DNA methylation at early AD stages compared to controls, involving ELOVL2, GIT1/TP53I13 and the histone gene locus at chromosome 6. DNA methylation levels assessed by bisulphite pyrosequencing correlated with phospho-tau protein burden for ELOVL2 and HIST1H3E/HIST1H3 F genes. In this discovery study, a set of four epigenetic marks of early AD stages have been identified in the human hippocampus. It would be worth studying in-depth the specific pathways related to these epigenetic marks. These early alterations in DNA methylation in the AD hippocampus could be regarded as candidate biomarkers to be explored in future translational studies. Abbreviations AD: Alzheimer’s disease; DMPs: Differentially methylated positions; CSF: Cerebrospinal fluid; βA42: β-amyloid 42; PET: positron emission tomography; 5mC: 5-methyl cytosine; CpG: cytosine-guanine dinucleotides; ANK1: ankyrin-1; BIN1: amphiphysin II; p-tau: hyperphosphorylated tau; CERAD: Consortium to Establish A Registry for Alzheimer’s Disease; SD: standard deviation; ANOVA: one-way analysis of variance; VLCFAs: very long-chain fatty acids; DHA: docosahexaenoic acid; mTOR: mechanistic target of rapamycin.

Characterization of the chromatin accessibility in Alzheimer’s disease

Previous studies showed that the pathological hallmarks of Alzheimer’s disease (AD) are characterized by β‐amyloid(Aβ) deposition, neurofibrillary tangles, the upregulation of inflammation and neuronal apoptosis. However, the molecular mechanisms of most genes participated in the pathways above remained unclear. Gene expression is associated with the transcriptional level which is decided by the chromatin accessibility. In this study, the landscape of chromatin accessibility was described to disclose the outline of the transcriptions of AD‐associated metabolism and gene expression in an AD mouse model.The assay for transposase‐accessible chromatin by sequencing (ATAC‐seq) was utilized to investigate the AD‐associated chromatin reshaping in APPswe/PS1dE9 AD mouse model. The ATAC‐seq data in the hippocampus of 8‐month‐old APP/PS1 mice was generated and the relationship between the chromatin accessibility and the gene expressions was analyzed in combination with RNA‐seq. Gene ontology (GO) analysis and KEGG were applied to facilitate elucidating the alteration of biological process and signaling pathways. In addition, critical transcription factors were identified and, the alteration of the chromatin accessibility was further confirmed using ChIP assays.The genomic location distribution of peaks showed that the peaks distributed on the promoter‐TSS regions of APP/PS1 mice is significantly more than WT mice and, 1690 AD‐associated chromatin accessible regions in the hippocampus tissues of APP/PS1 mice were identified. These regions were enriched in the signaling pathways included PI3K‐Akt signaling pathway, Hippo signaling pathway, TGF‐β signaling pathway and Jak‐Stat signaling pathway which play essential roles in regulating of cell proliferation, cell apoptosis and inflammatory. GO analysis showed that many AD‐associated biological processes declined including cellular response to hyperoxia and insulin stimulus, synaptic transmission, and positive regulation of autophagy. 1090 genes were found to be up‐regulated, and 1081 genes were found to be down‐regulated in the hippocampus of the AD model mice. Interestingly, enhanced ATAC‐seq signal were found around 740 genes, of which 43 genes exhibited up‐regulated mRNA level. Several most significantly increased genes were also identified, including Sele, Clec7a, Cst7 and Ccr6 which critically involved in the development of AD. In addition, a great deal of transcription factors, including Olig2, NeuroD1, TCF4, NeuroG2 were found to enrich in the AD‐associated accessible chromatin regions. Besides, the transcription‐activating marks of H3K4me3 and H3K27ac were increased in the promoters of Sele, Clec7a, Cst7 and Ccr6 gene. These results above indicates that the mechanism for the up‐regulation genes could attribute to the enrichment of open chromatin regions by transcription factors and histone marks H3K4me3 and H3K27ac.Altogether, our study reveals that the alterations of chromatin accessibility might be an initial mechanism in AD pathogenesis.Support or Funding InformationThis work was supported by grants from the National Natural Science Foundation of China (No.81430037, No.81871714) and the Beijing Postdoctoral Sustentation Fund of China (No.ZZ2019‐13).ATAC‐seq chromatin accessibility analysis in hippocampus of Alzheimer’s disease (AD) model mice. A. Distribution of chromatin‐accessible regions across the genome in AD and WT mice. B. Signaling pathway associated with chromatin accessibility in AD mice. C. GO analysis of biological process associated with accessible chromatin regions in AD mice. D. Venn diagram showing genes associated with the chromatin‐accessible regions in AD and differentially‐expressed genes.Figure 1Motif enrichment and Histone modifications at the accessible chromatin regions. A. The 15 motifs with the greatest enrichment. B. The fold changes of histone H3K4me3 and H3K27ac are determined by ChIP‐qPCR, in chromatin‐accessible regions of SELE, Ccr6, CD300lf, Clec7a and Cst7 genes. Data are shown as mean ± SD. *p<0.05 and **p<0.01.Figure 2

Correlation of Neural Oscillations during Stroop Testing with Hippocampal and Amygdala Volume differ between Cognitively Healthy Normal Aging and Pre‐symptomatic Alzheimer’s Disease

Background and ObjectivesStroop interference differences have been reported in the early stage of pre‐symptomatic Alzheimer’s disease (AD). The two most reported brain regions in AD (hippocampus and amygdala) haven’t been studied for interference processsing in the early AD stage. We aim to explore the relationship between brain interference processing and volumetric analysis on hippocampus and amygdala to understand the underlying neural events in pre‐symptomatic AD.MethodsWe employed a quantitative electroencephalography (qEEG) test to investigate brain activity during the Stroop interference test in a pre‐symptomatic AD study. Participants were instructed to name the color of the ink when the word and color match (congruent trials (CT)) or do not match (incongruent trials (IT)). Elderly study participants with normal cognition were recruited from the local community, consisting of two subgroups according to their cerebrospinal fluid proteins: cognitively healthy with normal amyloid/tau ratio (CH‐NAT, n=20) or pathological amyloid/tau ratio (CH‐PAT, n=21) between 60–95 years of age. A subgroup of the participants went through MRI scanning (9 CH‐NATs and 9 CH‐PATs) to obtain anatomical structures. They are age, gender, BMI, education balanced. We explored correlations between qEEG spectral power (2–30Hz) at six brain regions (frontal (F), central (C), parietal (P), left temporal (LT), right temporal (RT), and occipital (O)), and the magnetic resonance imaging (MRI) volumetric measures of two brain regions that most relate to Alzheimer’s disease: hippocampus and amygdala.Results & DiscussionIn CH‐NATs but not CH‐PATs, hippocampal volume is negatively correlated with early beta power during incongruent trials (IT) (p=0.002~0.021, r=−0.87~ −0.75), and early alpha power (p=0.0004~0.020, r=−0.92~ −0.75) over F,C,P,LT,RT regions. However, in CH‐PATs but not CH‐NATs, hippocampal volume is positively correlated with both early and late delta power during incongruent trials (IT) (p=0.001~0.042, r=0.68~0.90) over C,LT,RT,O regions.In CH‐NATs but not CH‐PATs, amygdala volume is negatively correlated with early alpha power (p=0.0003~0.0496, r=−0.93~ −0.67) on both CT (over F,C,LT,RT,O) and IT (over F,C,P,LT). However, CH‐PATs but not CH‐NATs, amygdala volume is positively correlated with late delta power during incongruent trials (IT) (p=0.007~0.023, r=0.74~0.82) over C,P,RT,O regions.The different correlations of qEEG with MRI between CH subgroups indicate maladaptive neuroplasticity already occurs in pre‐symptomatic AD stage. Previous studies have shown that amygdala atrophy is a prominent indicator of AD severity in patients including a potential relationship with aberrant motor behavior, anxiety, and irritability. We propose that early intervention strategies for pre‐symptomatic AD individuals that correct maladaptive neuroplasticity may attenuate neurodegeneration.Support or Funding InformationAcknowledgmentFinancial support provided by the L.K. Whittier Foundation, NIH R56 Funding 1R56AG063857‐01. Betty Chung and David Buennagel assisted with patient recruitment. Roger Rochart assisted with final draft.

Histological characterization of interneurons in Alzheimer's disease reveals a loss of somatostatin interneurons in the temporal cortex.

Neuronal dysfunction and synaptic loss are major hallmarks of Alzheimer's disease (AD) which correlate with symptom severity. Impairment of the γ-aminobutyric acid (GABA)ergic inhibitory interneurons, which form around 20% of the total neuronal network, may be an early event contributing to neuronal circuit dysfunction in neurodegenerative diseases. This study examined the expression of two of the main classes of inhibitory interneurons, parvalbumin (PV) and somatostatin (SST) interneurons in the temporal cortex and hippocampus of AD and control cases, using immunohistochemistry. We report a significant regional variation in the number of PV and SST interneurons with a higher number identified per mm2 in the temporal cortex compared to the hippocampus. Fewer SST interneurons, but not PV interneurons, were identified per mm2 in the temporal cortex of AD cases compared to control subjects. Our results support regional neuroanatomical effects on selective interneuron classes in AD, and suggest that impairment of the interneuronal circuit may contribute to neuronal dysfunction and cognitive decline in AD.