Aβ Plaque Formation Research Articles

Leptin peptides and the Implications on Alzheimer’s Disease

AbstractBackgroundObesity and neurodegeneration are growing health problems worldwide. Alzheimer’s disease (AD) is the most prevalent cause of progressive dementia in the elderly population. AD is characterized by the combined presence of extracellular plaques formed by β‐amyloid peptide and intraneuronal neurofibrillary tangles of abnormally hyperphosphorylated Tau protein. Several studies have shown that obesity is a risk factor for dementia. Leptin, initially described as the hormone responsible for controlling food intake and energy expenditure, also has other important physiological functions related to neuronal activity, proliferation and protection. With the discovery that neurogenesis persists in the brain of adult mammals, including brain regions affected by AD, many studies aim to stimulate this physiological process in various areas of the brain for the treatment of neurodegenerative diseases to repair and/or prevent neural loss. These regions also express the long form of the LepRb leptin receptor and are the first regions to be affected by chronic neurocognitive deficits.MethodGiven the neurogenic potential of leptin, the main objective of this study is to analyze and compare the action of this hormone with synthetic peptides (PEP) on cell proliferation, differentiation and Aβ plaque formation in two of the main neurogenic niches in AD model mice.ResultThe expression of glial, neuoblast and Aβ markers were detected by immunohistochemistry. We observed that animals treated with PEP4 had a significant increase in the proportion of BrdU/DCX+ cells regardless the age and animal model. Our results also show that treatment with PEP4 was able to significantly decrease the amount of Aβ plaques in the hippocampus of AD model animals. However, it is observed that this decrease is significantly smaller than when compared to that produced by leptin, demonstrating that it is more effective in reducing the number of Aβ plaques in the hippocampus region.ConclusionWe believe that a better understanding of the mechanisms of the pathological processes that cause AD and how altered leptin signaling affects these processes could lead to the development of early therapies for the treatment of Alzheimer’s disease.

Phospholipase D3 drives microglial response to amyloid pathology in Alzheimer’s disease

AbstractBackgroundAmyloid‐beta (Aβ) plaque formation is a well‐established hallmark for Alzheimer’s disease (AD). However, the processes behind plaque formation are not understood. Previous work from our group identified rare coding variants for PLD3, with one variant in particular, p.A442A, disrupting a splicing enhancer binding site within the mRNA transcript. In this study, we present findings that PLD3 regulates Aβ clearance in the brain through both cell autonomous and non‐autonomous means.MethodTo replicate the splicing effect observed in patient brain samples in vitro, PLD3 p.A442A expressing induced pluripotent stem cells (iPSCs) were differentiated into neurons or microglia and evaluated for extracellular Aβ and Aβ uptake, respectively. In an APP/PSEN1xPld3KO mouse model, Aβ dynamics were assessed with in vivo microdialysis and plaque pathology was assessed with immunohistochemistry. Frozen cortical tissue from these mice was analyzed through bulk RNAseq to identify transcriptomic and molecular changes that are attributed to Pld3 deficiency. PLD3 expression was assessed in an independent single‐cell RNAseq (scRNAseq) dataset from iPSC‐derived microglia to assess a potential cell‐autonomous role for PLD3 in microglia.ResultTranscriptomics from human samples reveal a significant decrease of PLD3 expression in AD brains versus controls, particularly in the brain regions most susceptible to amyloid pathology. Similar to PLD3‐variant brains, iPSC‐derived neurons carrying PLD3 p.A442A exhibited alternative splicing and displayed elevated Aβ levels in the conditioned media. Loss of Pld3 in APP/PSEN1 mice led to increased interstitial levels of Aβ and reduced Aβ clearance. Immunohistochemistry revealed an increase in diffuse, nonfibrillar plaque area and reduced microglial recruitment in APP/PSEN1xPld3KO. Transcriptomics data from brain tissue in these mice revealed altered expression of genes that define the disease associated microglia signatures. To begin to understand the role of PLD3 in microglia, we analyzed scRNAseq from CRISPRi screen in iPSC‐derived microglia. We found that PLD3 expression is enriched in interferon‐associated microglia. Finally, we demonstrate that iPSC‐derived microglia carrying PLD3 p.A442A exhibit reduced internalization of Aβ and myelin, suggesting a defect in phagocytic capacity.ConclusionTogether, we show that PLD3 plays a critical role in the brain by facilitating the microglial response to Aβ plaque pathology, modulating plaque composition.

Safety, tolerability, pharmacokinetics and pharmacodynamics of a single intravenous dose of SHR‐1707 in healthy adult subjects: two randomized, double‐blind, phase 1 studies

AbstractBackgroundSHR‐1707 is a novel humanized anti‐Aβ IgG1 monoclonal antibody that binds to Aβ fibrils and monomers to block the formation of Aβ plaques and to promote the microglial phagocytosis of Aβ. Preclinical studies in 5xFAD transgenic mice showed that SHR‐1707 reduced brain Aβ deposition and ameliorated memory deficits. Herein, we conducted two phase 1 studies to evaluate the safety, tolerability, pharmacokinetics (PK) and pharmacodynamics (PD) of a single intravenous dose of SHR‐1707 in healthy adult subjects.MethodTwo randomized, double‐blind, single‐ascending‐dose, phase 1 studies were conducted in China (Study CHN; NCT04973189) and Australia (Study AUS; NCT04745104). Study CHN consisted of 2 parts. In part 1, eligible healthy young adults (18‐45 years) were sequentially randomized 8:2 to receive SHR‐1707 (5 cohorts: 2, 6, 20, 40, and 60 mg/kg) or placebo in each cohort; in part 2, elderly subjects (55‐80 years) were randomized 8:4 to receive SHR‐1707 (20 mg/kg) or placebo. A similar design was used in Study AUS, but with only healthy young adults enrolled across 3 dosing cohorts (2, 20, and 60 mg/kg).Result62 (part 1/2, n = 50/12; mean age, 27.0/57.2 years) and 30 subjects (mean age, 26.1 years) were treated in Study CHN and Study AUS respectively. In Study CHN, across all dose levels, all TRAEs were mild in severity, with the most common being laboratory abnormalities. In Study AUS, TRAEs were mostly mild (1 moderate event each with SHR‐1707/placebo); the most common TRAEs with SHR‐1707 were dysgeusia and fatigue (8.3% each). In both studies, the exposure of SHR‐1707 increased in a slightly greater than dose‐proportional manner over the dose range of 2‐60 mg/kg in young adults; there was a dose‐dependent increase in plasma Aβ42 concentration following SHR‐1707 administration compared with the placebo group. The safety and PK/PD profiles of SHR‐1707 in the elderly subjects were consistent with the younger counterpart at the same dose level. No ethnic difference in safety and PK/PD of SHR‐1707 was observed.ConclusionA single intravenous dose of SHR‐1707 at 2‐60 mg/kg was safe and well tolerated in healthy young adult and elderly subjects. The PK/PD profiles are supportive of further clinical development.

Seed‐competent, high‐molecular‐weight Aβ species is abundantly extracted in the cerebrovasculature and meninges in Alzheimer’s disease

AbstractBackgroundSoluble high‐molecular‐weight (HMW) amyloid β (Aβ) species extracted from autopsied brains of patients with Alzheimer’s disease (AD) have been demonstrated to exhibit a seeding potency to induce cerebral β‐amyloidosis. However, it remains unknown where Aβ seed species resides and how it propagates throughout human AD brains. Our objective is to detect Aβ seed in human AD brain cerebrovasculature and meninges that are enriched with cerebral amyloid angiopathy (CAA).MethodWe examined eight autopsied human AD brains with abundant CAA and eight AD brains without immunohistochemically detectable CAA. Tris‐buffered saline (TBS)‐soluble fractions from the brain parenchyma or meningeal tissues were separated by size‐exclusion chromatography (SEC) with Superdex 75 column, and the concentrations of Aβ in each SEC‐separated fraction were measured by enzyme‐linked immunosorbent assay (ELISA). The TBS‐soluble, high‐molecular‐weight Aβ‐positive fractions were stereotaxically injected into the unilateral hippocampus or cisterna magna of 3‐month‐old amyloid precursor protein (APP) transgenic (tg) mice, and Aβ deposition in the hippocampus was assessed after four months.ResultHMW Aβ species were detected in TBS‐soluble fractions of the meninges and cerebrovasculature isolated from human AD brains. The concentration of HMW Aβ species extracted from meninges and cerebrovasculature was significantly higher than that from brain parenchyma in the same cases. Meningeal HMW Aβ species induced a robust Aβ deposition in the hippocampus, the area of which was significantly higher than that from the same weight of brain parenchyma. Moreover, the concentration of HMW Aβ species in CAA‐rich AD brains with meninges removed was significantly higher than those of CAA‐minimal AD brains. Intracisternal injection of HMW Aβ species derived from human AD brains induced not only CAA but also Aβ plaque.ConclusionSeed competent Aβ species are more abundant in cerebrovasculature and meninges than in brain parenchyma, and may accumulate in CAA in human AD brains. The possibility that HMW Aβ species in CAA contributes to Aβ plaque formation warrants further investigation in future studies.

Mistranslation-associated perturbations of proteostasis do not promote accumulation of amyloid beta and plaque deposition in aged mouse brain

A common perception in age-related neurodegenerative diseases posits that a decline in proteostasis is key to the accumulation of neuropathogenic proteins, such as amyloid beta (Aβ), and the development of sporadic Alzheimer’s disease (AD). To experimentally challenge the role of protein homeostasis in the accumulation of Alzheimer’s associated protein Aβ and levels of associated Tau phosphorylation, we disturbed proteostasis in single APP knock-in mouse models of AD building upon Rps9 D95N, a recently identified mammalian ram mutation which confers heightened levels of error-prone translation together with an increased propensity for random protein aggregation and which is associated with accelerated aging. We crossed the Rps9 D95N mutation into knock-in mice expressing humanized Aβ with different combinations of pathogenic mutations (wild-type, NL, NL-F, NL-G-F) causing a stepwise and quantifiable allele-dependent increase in the development of Aβ accumulation, levels of phosphorylated Tau, and neuropathology. Surprisingly, the misfolding-prone environment of the Rps9 D95N ram mutation did not affect Aβ accumulation and plaque formation, nor the level of phosphorylated Tau in any of the humanized APP knock-in lines. Our findings indicate that a misfolding-prone environment induced by error-prone translation with its inherent perturbations in protein homeostasis has little impact on the accumulation of pathogenic Aβ, plaque formation and associated phosphorylated Tau.

Polyherbal and Multimodal Treatments: Kaempferol- and Quercetin-Rich Herbs Alleviate Symptoms of Alzheimer's Disease.

Alzheimer's Disease (AD) is a progressive neurodegenerative disorder impairing cognition and memory in the elderly. This disorder has a complex etiology, including senile plaque and neurofibrillary tangle formation, neuroinflammation, oxidative stress, and damaged neuroplasticity. Current treatment options are limited, so alternative treatments such as herbal medicine could suppress symptoms while slowing cognitive decline. We followed PRISMA guidelines to identify potential herbal treatments, their associated medicinal phytochemicals, and the potential mechanisms of these treatments. Common herbs, including Ginkgo biloba, Camellia sinensis, Glycyrrhiza uralensis, Cyperus rotundus, and Buplerum falcatum, produced promising pre-clinical results. These herbs are rich in kaempferol and quercetin, flavonoids with a polyphenolic structure that facilitate multiple mechanisms of action. These mechanisms include the inhibition of Aβ plaque formation, a reduction in tau hyperphosphorylation, the suppression of oxidative stress, and the modulation of BDNF and PI3K/AKT pathways. Using pre-clinical findings from quercetin research and the comparatively limited data on kaempferol, we proposed that kaempferol ameliorates the neuroinflammatory state, maintains proper cellular function, and restores pro-neuroplastic signaling. In this review, we discuss the anti-AD mechanisms of quercetin and kaempferol and their limitations, and we suggest a potential alternative treatment for AD. Our findings lead us to conclude that a polyherbal kaempferol- and quercetin-rich cocktail could treat AD-related brain damage.

Pincer Ligands as Multifunctional Agents for Alzheimer's Copper Dysregulation and Oxidative Stress: A Computational Evaluation.

Alzheimer's disease (AD) is the most common form of dementia worldwide, affecting millions of people around the globe. AD is characterized by different pathologies being beta-amyloid (Aβ) plaque formation, metal ion dysregulation, and oxidative stress (OS) central topics under investigation. Copper-Aβ complexes have been shown to induce catalytic hydrogen peroxide formation and increase OS in the brain leading to neuronal death. Pincer-type compounds are tridentate ligands that coordinate metals in a planar fashion whose properties can be tuned via group substitutions, giving rise to many possibilities in catalysis and drug discovery. In this work we evaluated the potential pharmaceutical activity of 26 pincer compounds in AD's copper ion-related oxidative stress framework. In this sense, four key aspects were considered: 1) Lipinski's rule of five, 2) blood-brain barrier permeation, 3) standard reduction potential (SRP) of the formed copper complexes, and 4) the ligand's affinity towards copper cations. The evaluation of these criteria was performed by means of bioinformatic tools and electronic structure calculations at the DFT level of theory. Our results suggest that two compounds from this set are potential antioxidant agents, whereas five of them are promissory distributor-like compounds in the context of AD.

Intermittent hypoxia therapy ameliorates beta-amyloid pathology via TFEB-mediated autophagy in murine Alzheimer's disease

BackgroundAlzheimer's disease (AD) is the most prevalent neurodegenerative disorder. Impaired autophagy in plaque-associated microglia (PAM) has been reported to accelerate amyloid plaque deposition and cognitive impairment in AD pathogenesis. Recent evidence suggests that the transcription factor EB (TFEB)-mediated activation of the autophagy–lysosomal pathway is a promising treatment approach for AD. Moreover, the complementary therapy of intermittent hypoxia therapy (IHT) has been shown to upregulate autophagy and impart beneficial effects in patients with AD. However, the effect of IHT on PAM remains unknown.Methods8-Month-old APP/PS1 mice were treated with IHT for 28 days. Spatial learning memory capacity and anxiety in mice were investigated. AD pathology was determined by the quantity of nerve fibers and synapses density, numbers of microglia and neurons, Aβ plaque deposition, pro-inflammatory factors, and the content of Aβ in the brain. TFEB-mediated autophagy was determined by western blot and qRT-PCR. Primary microglia were treated with oligomeric Aβ 1–42 (oAβ) combined with IHT for mechanism exploration. Differential genes were screened by RNA-seq. Autophagic degradation process of intracellular oAβ was traced by immunofluorescence.ResultsIn this study, we found that IHT ameliorated cognitive function by attenuating neuronal loss and axonal injury in an AD animal model (APP/PS1 mice) with beta-amyloid (Aβ) pathology. In addition, IHT-mediated neuronal protection was associated with reduced Aβ accumulation and plaque formation. Using an in vitro PAM model, we further confirmed that IHT upregulated autophagy-related proteins, thereby promoting the Aβ autophagic degradation by PAM. Mechanistically, IHT facilitated the nuclear localization of TFEB in PAM, with TFEB activity showing a positive correlation with Aβ degradation by PAM in vivo and in vitro. In addition, IHT-induced TFEB activation was associated with the inhibition of the AKT–MAPK–mTOR pathway.ConclusionsThese results suggest that IHT alleviates neuronal damage and neuroinflammation via the upregulation of TFEB-dependent Aβ clearance by PAM, leading to improved learning and memory in AD mice. Therefore, IHT may be a promising non-pharmacologic therapy in complementary medicine against AD.Graphical

Amyloid PET across the cognitive spectrum in former professional and college American football players: findings from the DIAGNOSE CTE Research Project

BackgroundExposure to repetitive head impacts (RHI) in American football players can lead to cognitive impairment and dementia due to neurodegenerative disease, particularly chronic traumatic encephalopathy (CTE). The pathognomonic lesion of CTE consists of perivascular aggregates of hyper-phosphorylated tau in neurons at the depths of cortical sulci. However, it is unclear whether exposure to RHI accelerates amyloid-β (Aβ) plaque formation and increases the risk for Alzheimer’s disease (AD). Although the Aβ neuritic plaques characteristic of AD are observed in a minority of later-stage CTE cases, diffuse plaques are more common. This study examined whether former professional and college American football players, including those with cognitive impairment and dementia, have elevated neuritic Aβ plaque density, as measured by florbetapir PET. Regardless of cognitive and functional status, elevated levels of florbetapir uptake were not expected.MethodsWe examined 237 men ages 45–74, including 119 former professional (PRO) and 60 former college (COL) football players, with and without cognitive impairment and dementia, and 58 same-age men without a history of contact sports or TBI (unexposed; UE) and who denied cognitive or behavioral symptoms at telephone screening. Former players were categorized into four diagnostic groups: normal cognition, subjective memory impairment, mild cognitive impairment, and dementia. Positive florbetapir PET was defined by cortical-cerebellar average SUVR of ≥ 1.10. Multivariable linear regression and analysis of covariance (ANCOVA) compared florbetapir average SUVR across diagnostic and exposure groups. Multivariable logistic regression compared florbetapir positivity. Race, education, age, and APOE4 were covariates.ResultsThere were no diagnostic group differences either in florbetapir average SUVR or the proportion of elevated florbetapir uptake. Average SUVR means also did not differ between exposure groups: PRO-COL (p = 0.94, 95% C.I. = [− 0.033, 0.025]), PRO-UE (p = 0.40, 95% C.I. = [− 0.010, 0.029]), COL-UE (p = 0.36, 95% CI = [0.0004, 0.039]). Florbetapir was not significantly associated with years of football exposure, cognition, or daily functioning.ConclusionsCognitive impairment in former American football players is not associated with PET imaging of neuritic Aβ plaque deposition. These findings are inconsistent with a neuropathological diagnosis of AD in individuals with substantial RHI exposure and have both clinical and medico-legal implications.Trial registrationNCT02798185.

Virtual histology of Alzheimer’s disease: Biometal entrapment within amyloid-[formula omitted] plaques allows for detection via X-ray phase-contrast imaging

Amyloid-β (Aβ) plaques from Alzheimer’s Disease (AD) can be visualized ex vivo in label-free brain samples using synchrotron X-ray phase-contrast tomography (XPCT). However, for XPCT to be useful as a screening method for amyloid pathology, it is essential to understand which factors drive the detection of Aβ plaques. The current study was designed to test the hypothesis that Aβ-related contrast in XPCT could be caused by Aβ fibrils and/or by metals trapped in the plaques. Fibrillar and elemental compositions of Aβ plaques were probed in brain samples from different types of AD patients and AD models to establish a relationship between XPCT contrast and Aβ plaque characteristics. XPCT, micro-Fourier-Transform Infrared spectroscopy and micro-X-Ray Fluorescence spectroscopy were conducted on human samples (one genetic and one sporadic case) and on four transgenic rodent strains (mouse: APPPS1, ArcAβ, J20; rat: TgF344). Aβ plaques from the genetic AD patient were visible using XPCT, and had higher β-sheet content and higher metal levels than those from the sporadic AD patient, which remained undetected by XPCT. Aβ plaques in J20 mice and TgF344 rats appeared hyperdense on XPCT images, while they were hypodense with a hyperdense core in the case of APPPS1 and ArcAβ mice. In all four transgenic strains, β-sheet content was similar, while metal levels were highly variable: J20 (zinc and iron) and TgF344 (copper) strains showed greater metal accumulation than APPPS1 and ArcAβ mice. Hence, a hyperdense contrast formation of Aβ plaques in XPCT images was associated with biometal entrapment within plaques. Statement of significanceThe role of metals in Alzheimer’s disease (AD) has been a subject of continuous interest. It was already known that amyloid-β plaques (Aβ), the earliest hallmark of AD, tend to trap endogenous biometals like zinc, iron and copper. Here we show that this metal accumulation is the main reason why Aβ plaques are detected with a new technique called X-ray phase contrast tomography (XPCT). XPCT enables to map the distribution of Aβ plaques in the whole excised brain without labeling. In this work we describe a unique collection of four transgenic models of AD, together with a human sporadic and a rare genetic case of AD, thus exploring the full spectrum of amyloid contrast in XPCT.

Early tactile stimulation influences the development of Alzheimer's disease in gestationally stressed APP NL-G-F adult offspring NL-G-F/NL-G-F mice

Alzheimer's disease (AD) is associated with cerebral plaques and tangles, reduced synapse number, and shrinkage in several brain areas and these morphological effects are associated with the onset of compromised cognitive, motor, and anxiety-like behaviours. The appearance of both anatomical and behavioural symptoms is worsened by stress. The focus of this study was to examine the effect of neonatal tactile stimulation on AD-like behavioural and neurological symptoms on APP NL-G-F/NL-G-F mice, a mouse model of AD, who have been gestationally stressed. Our findings indicate that neonatal tactile stimulation improves cognition, motor skills, and anxiety-like symptoms in both gestationally stressed and non-stressed adult APP mice and that these alterations are associated with reduced Aβ plaque formation. Thus, tactile stimulation appears to be a promising non-invasive preventative strategy for slowing the onset of dementia in aging animals.

An Exosome-Based Therapeutic Strategy Targeting Neuroinflammation in Alzheimer's Disease with Berberine and Palmatine.

Neuroinflammation is one of the major pathogeneses in Alzheimer's disease (AD) and mainly involves abnormal inflammatory activation of microglia by multiple pathological stimuli. The treatment of AD remains a major challenge due to the multifactorial characterization of AD and the inefficient ability of therapeutic drugs to permeate through the blood‒brain barrier (BBB). Accordingly, drug combination treatment and drug carrier delivery have become important therapeutic tools for the treatment of multifactorial diseases, especially AD. Inflammatory cytokine levels in microglia, including NO, TNF-α, IL-1β, IL-4, and IL-10, were detected. The Morris water maze and object location task were used to investigate the learning and memory functions of APP/PS1 mice in different treatment groups. The number of neurons and plasticity of synapses were evaluated by immunofluorescence double labelling. Additionally, the ratio of β-amyloid plaques and the number of activated microglia were evaluated by immunofluorescence staining. The concentrations of β-amyloid plaques and inflammatory factors in the hippocampus were determined by ELISA. Microglia-derived exosomes (Exos) were extracted and purified by size exclusion chromatography. The distribution of exosomes and drugs was investigated in vitro and in vivo. Compared to single drug interventions, the combination of Ber and Pal (Ber/Pal) modulated microglial inflammatory cytokine levels. Ber/Pal promoted the recovery of learning and memory impairment in APP/PS1 mice. Immunofluorescence staining indicated that Ber/Pal restored neurons, inhibited Aβ plaque formation and microglial activation, and regulated the secretion of inflammatory factors. Exos promoted the accumulation of drugs in cells and tissues and improved the targeting of drugs across the BBB. Ber/Pal could offer a synergistic and more comprehensive therapeutic effect in AD. Additionally, the microglia-derived Exos-Ber/Pal delivery system promoted the targeting and permeation of drugs into the brain, suggesting a creative strategy for targeting AD therapy by regulating neuroinflammation in microglial cells.

The Crystal Structure of the Hsp90-LA1011 Complex and the Mechanism by Which LA1011 May Improve the Prognosis of Alzheimer's Disease.

Functional changes in chaperone systems play a major role in the decline of cognition and contribute to neurological pathologies, such as Alzheimer's disease (AD). While such a decline may occur naturally with age or with stress or trauma, the mechanisms involved have remained elusive. The current models suggest that amyloid-β (Aβ) plaque formation leads to the hyperphosphorylation of tau by a Hsp90-dependent process that triggers tau neurofibrillary tangle formation and neurotoxicity. Several co-chaperones of Hsp90 can influence the phosphorylation of tau, including FKBP51, FKBP52 and PP5. In particular, elevated levels of FKBP51 occur with age and stress and are further elevated in AD. Recently, the dihydropyridine LA1011 was shown to reduce tau pathology and amyloid plaque formation in transgenic AD mice, probably through its interaction with Hsp90, although the precise mode of action is currently unknown. Here, we present a co-crystal structure of LA1011 in complex with a fragment of Hsp90. We show that LA1011 can disrupt the binding of FKBP51, which might help to rebalance the Hsp90-FKBP51 chaperone machinery and provide a favourable prognosis towards AD. However, without direct evidence, we cannot completely rule out effects on other Hsp90-co-chaprone complexes and the mechanisms they are involved in, including effects on Hsp90 client proteins. Nonetheless, it is highly significant that LA1011 showed promise in our previous AD mouse models, as AD is generally a disease affecting older patients, where slowing of disease progression could result in AD no longer being life limiting. The clinical value of LA1011 and its possible derivatives thereof remains to be seen.

The novel visual cognitive assessment test correlates well with plasma oligomeric amyloid beta in patients with mild cognitive impairment

AbstractBackgroundOligomeric Amyloid Beta (OAβ), is representative of a soluble, neurotoxic and pathogenic form of Aβ, which has been found to function as upstream drivers of Alzheimer’s Disease pathology (Tolar et al., 2021). It serves as a contributory factor towards the formation of cortical Aβ plaques and neurofibrillary Tau tangles, and has been found to induce oxidative stress, synaptic toxicity and neuroinflammation (Tolar et al., 2021). The pathology culminates in neuronal dysfunction/death and resultant neurodegeneration which has been found to manifest clinically as symptoms of cognitive decline. OAβ has been found to correlate with the severity of cognitive performance, as well as brain volume reduction (An et al., 2017, Wang et al., 2017, Meng et al., 2019, Youn et al., 2019, Babapour Mofrad et al., 2021). Nevertheless, its effect on language neutral cognitive tests ‐ the novel Visual Cognitive Assessment Test (VCAT) developed and validated by our team of neurologist and neuropsychologists; remains to be evaluated (Kandiah et al., 2016, Lim et al., 2018, Low et al., 2020).MethodsA cross‐sectional pilot study was conducted in a cohort of 63 patients, clinically diagnosed with mild cognitive impairment (MCI). The patients underwent cognitive evaluation tests, Multimer Detection System (MDS) based plasma OAβ analysis and MRI based cortical grey matter evaluations (Wang et al., 2017, Youn et al., 2019, Pyun et al., 2021, Vipin et al., 2021). Pearson’s correlation evaluated associations between plasma OAβ, cognitive scores [Mini‐Mental State Examination (MMSE), VCAT] and brain volume measures [Grey Matter Volume (GMV) / Intracranial Volume (ICV)].ResultsIncreasing plasma OAβ expression associated with decreasing, VCAT scores (r = ‐0.291, 95% CI = ‐0.504 to ‐0.044, p = 0.022) and MMSE scores (r = ‐0.272, 95% CI = ‐0.489 to ‐0.024, p = 0.032), in MCI patients (Figure 1A, B). Additionally increasing plasma OAβ expression also associated with decreasing and GMV/ ICV ratio (r = ‐0.264, 95% CI = ‐0.489 to ‐0.007, p = 0.045), in MCI patients (Figure 1C).ConclusionFindings from this study, emphasise on the promising clinical utility of plasma OAβ as a biomarker. Future longitudinal studies will validate these associations across the Alzheimer’s disease spectrum.

Anti‐amyloid beta and anti‐acetylcholinesterase activity of Anaphalis neelgerriana leaves extract in streptozotocin induced Alzheimer rats

AbstractBackgroundAlzheimer is associated with neuronal degeneration, characterized by memory loss and altered behaviour. Many pathological conditions like increased amyloid β (Aβ) plaque formation, and acetylcholinesterase neuroinflammation results in AD. Due to excess of reactive oxygen species (ROS) oxidative stress develops which overexpress Aß in the neuron which modifies the cellular function and thereby activates the neurodegeneration.MethodAD was induced by streptozotocin i.e. STZ (3 mg/kg, ICV) day 1st and 3rd day after surgery. Surgery was done on anesthetized rats by the help of stereotaxic apparatus. STZ induced AD rats were treated with ethanolic extracts of Anaphalis neelgerriana leaves (ANLE) (100 and 200 mg/kg, p.o.) for 14 days. Effects of ANLE in Alzheimer diseased rats were assessed for amyloid β peptide (Aβ) and acetylcholinesterase (AchE)ResultANLE significantly (p<0.01) decreases the Aβ1‐40, Aβ1‐42 peptides. Acetylcholinesterase level in the rat’s brain tissue reduced compared to Alzheimer diseased rats.ConclusionThe present study reveals that the ANLE produces Anti‐Alzheimer’s effect in Alzheimer diseased rats by decreasing Aβ protein level and Acetylcholinesterase level in the brain tissue.

FLAIR MRI biomarkers of the Normal‐Appearing Brain Matter (NABM) are related to APOE‐4 status and CSF markers Aβ42 and Tau

AbstractBackgroundReduced amyloid‐beta‐42 (Aβ42) and elevated total tau (t‐tau) protein concentrations in the CSF are characteristic of Alzheimer’s disease (AD) pathology [1]. Aβ42 contributes to extracellular plaque formation between neurons [2]. The total level of tau, a microtubule‐stabilizer in neuron axons [3], is associated with neuronal death [1]. Additionally, presence of ApoE4 (ε4) alleles is an established identifier for increased risk of AD [4]. Non‐invasive imaging‐based correlates of the CSF markers are lacking. This study examines correlations of novel FLAIR texture, intensity, and volume biomarkers, along with white matter lesion (WML) burden, with Aβ42, t‐tau, and ε4 status.MethodFLAIR volumes (n = 4044) from the ADNI database were used for analysis with CSF biomarkers. A subset (n = 921) was used for ε4 analysis based on available data. Normal‐appearing brain matter (NABM) was obtained by removing CSF and WML. Macrostructural damage (MAD), microstructural damage (MID), and integrity (MII) texture biomarkers [5] were extracted from each NABM volume (Fig. 1), along with median intensity, NABM/ICV ratio, and normalized WML volume [5]. Relationships between FLAIR biomarkers and AD markers were described using parametric statistical analyses. Statistical significance was set at p<0.05.ResultAll FLAIR biomarkers were statistically significantly correlated with CSF Aβ42 levels. All features except MID and WML burden were significantly correlated with CSF t‐tau levels (Table 1). MAD, MID, and WML burden showed negative correlations with Aβ42, while MAD showed a positive correlation with t‐tau. Opposite trends were seen with MII, intensity, and NABM/ICV (Fig. 2). Significant differences between groups without and with one ε4 allele were found in all FLAIR biomarkers except WML burden. Significant differences in MAD, MII and NABM/ICV were found between groups with one and two ε4 alleles (Table 2).ConclusionFLAIR biomarkers were inversely associated with CSF Aβ42 concentrations, suggesting they may be surrogate markers of Aβ plaque formation. They were associated with CSF t‐tau concentrations, suggesting they could also be indicators of GM degeneration and neuronal death. They could also be indicators for patients at increased risk of AD, as they demonstrated significant differences with the presence of ε4. Further longitudinal studies are required to establish the exact mechanism of neurodegeneration.

ELUCIDATING THE COMBINED EFFECTS OF AMYLOID AND TAU IN A NOVEL BIGENIC RAT MODEL WITH HUMAN ALZHEIMER’S DISEASE‐LIKE PATHOLOGY

AbstractBackgroundBoth amyloid beta (Aβ) and tau pathologies co‐exist in Alzheimer’s disease. While studies have shown that Aβ and tau interaction results in elevated AD pathology, it is not clearly understood how they might affect one another during early pathology stages leading to Aβ plaque formation. This study aimed at determining how and to which extent a combination of gradually developing amyloid and tau pathologies exacerbate each other in the context of Alzheimer’s disease‐like pathology in a novel transgenic rat model.MethodsHeterozygous McGill‐R‐Thy1‐APP and R955‐hTau single transgenic rats were crossed, producing a novel bigenic rat model with both human amyloid and tau pathologies, named McGill‐R‐APPxhTau955. Bigenic rats express human APP with the Swedish and Indiana mutations (KM670/671NL, V717F) as well as the longest isoform of human tau (2N4R) with the P301S mutation causative of frontotemporal dementia. Transgenic rats (n = 10‐12) were raised to cohorts at 12, 20 and 24 months of age and were subject to a battery of behavioural testing for cognition. Examination of amyloid and tau pathology, as well as inflammatory and neurodegenerative processes, was performed primarily using immunohistochemistry (IHC) and Western blot (WB). Levels of amyloid, tau and p‐tau were measured in CSF, brain and blood serum by electrochemiluminescence immunoassays. Bigenic animals were compared to single transgenics and wild‐type littermate controls.ResultsAPPxR955‐hTau bigenic rats produced a gradual accumulation of human amyloid and tau, resulting in progressive cognitive deficits and Alzheimer‐like pathology. We discovered that tau accumulation produced a compensatory effect on cognition and long‐term potentiation at 20 months, rescuing amyloid‐induced cognitive effects. However, at 24 months of age, bigenic rats displayed worsened cognition compared to single transgenics in spatial learning and memory. Reflective of these findings, bigenic rats developed an increased phosphorylaton of tau at 24 months and increased Aβ plaque pathology. Status of biomarker levels, neuroinflammation and neurodegeneration are actively under investigation and are expected to trend similarly.ConclusionsThe McGill‐R‐APPxhTau novel bigenic rat, developing slow progressing amyloid and tau pathologies, is an attractive model for the further investigation of mechanisms by which both proteins effect one another, the observation of biomarker changes and elucidation of early disease stages.

Myelin dysfunction drives amyloid-β deposition in models of Alzheimer’s disease

The incidence of Alzheimer’s disease (AD), the leading cause of dementia, increases rapidly with age, but why age constitutes the main risk factor is still poorly understood. Brain ageing affects oligodendrocytes and the structural integrity of myelin sheaths1, the latter of which is associated with secondary neuroinflammation2,3. As oligodendrocytes support axonal energy metabolism and neuronal health4–7, we hypothesized that loss of myelin integrity could be an upstream risk factor for neuronal amyloid-β (Aβ) deposition, the central neuropathological hallmark of AD. Here we identify genetic pathways of myelin dysfunction and demyelinating injuries as potent drivers of amyloid deposition in mouse models of AD. Mechanistically, myelin dysfunction causes the accumulation of the Aβ-producing machinery within axonal swellings and increases the cleavage of cortical amyloid precursor protein. Suprisingly, AD mice with dysfunctional myelin lack plaque-corralling microglia despite an overall increase in their numbers. Bulk and single-cell transcriptomics of AD mouse models with myelin defects show that there is a concomitant induction of highly similar but distinct disease-associated microglia signatures specific to myelin damage and amyloid plaques, respectively. Despite successful induction, amyloid disease-associated microglia (DAM) that usually clear amyloid plaques are apparently distracted to nearby myelin damage. Our data suggest a working model whereby age-dependent structural defects of myelin promote Aβ plaque formation directly and indirectly and are therefore an upstream AD risk factor. Improving oligodendrocyte health and myelin integrity could be a promising target to delay development and slow progression of AD.

Neuroplastin 65 deficiency reduces amyloid plaque formation and cognitive deficits in an Alzheimer's disease mouse model.

Alzheimer's disease (AD) is characterized by increasing cognitive dysfunction, progressive cerebral amyloid beta (Aβ) deposition, and neurofibrillary tangle aggregation. However, the molecular mechanisms of AD pathologies have not been completely understood. As synaptic glycoprotein neuroplastin 65 (NP65) is related with synaptic plasticity and complex molecular events underlying learning and memory, we hypothesized that NP65 would be involved in cognitive dysfunction and Aβ plaque formation of AD. For this purpose, we examined the role of NP65 in the transgenic amyloid precursor protein (APP)/presenilin 1 (PS1) mouse model of AD. Neuroplastin 65-knockout (NP65-/-) mice crossed with APP/PS1 mice to get the NP65-deficient APP/PS1 mice. In the present study, a separate cohort of NP65-deficient APP/PS1 mice were used. First, the cognitive behaviors of NP65-deficient APP/PS1 mice were assessed. Then, Aβ plaque burden and Aβ levels in NP65-deficient APP/PS1 mice were measured by immunostaining and western blot as well as ELISA. Thirdly, immunostaining and western blot were used to evaluate the glial response and neuroinflammation. Finally, protein levels of 5-hydroxytryptamin (serotonin) receptor 3A and synaptic proteins and neurons were measured. We found that loss of NP65 alleviated the cognitive deficits of APP/PS1 mice. In addition, Aβ plaque burden and Aβ levels were significantly reduced in NP65-deficient APP/PS1 mice compared with control animals. NP65-loss in APP/PS1 mice resulted in a decrease in glial activation and the levels of pro- and anti-inflammatory cytokines (IL-1β, TNF-α, and IL-4) as well as protective matrix YM-1 and Arg-1, but had no effect on microglial phenotype. Moreover, NP65 deficiency significantly reversed the increase in 5-hydroxytryptamine (serotonin) receptor 3A (Htr3A) expression levels in the hippocampus of APP/PS1 mice. These findings identify a previously unrecognized role of NP65 in cognitive deficits and Aβ formation of APP/PS1 mice, and suggest that NP65 may serve as a potential therapeutic target for AD.

Mass Spectrometry Imaging in Alzheimer's Disease.

Introduction: Amyloid-beta (Aβ) pathology is the precipitating histopathological characteristic of Alzheimer's disease (AD). Although the formation of amyloid plaques in human brains is suggested to be a key factor in initiating AD pathogenesis, it is still not fully understood the upstream events that lead to Aβ plaque formation and its metabolism inside the brains. Methods: Matrix-assisted laser desorption ionization mass spectrometry imaging (MALDI-MSI) has been successfully introduced to study AD pathology in brain tissue both in AD mouse models and human samples. By using MALDI-MSI, a highly selective deposition of Aβ peptides in AD brains with a variety of cerebral amyloid angiopathy (CAA) involvement was observed. Results: MALDI-MSI visualized depositions of shorter peptides in AD brains; Aβ1-36 to Aβ1-39 were quite similarly distributed with Aβ1-40 as a vascular pattern, and deposition of Aβ1-42 and Aβ1-43 was visualized with a distinct senile plaque pattern distributed in parenchyma. Moreover, how MALDI-MSI covered in situ lipidomics of plaque pathology has been reviewed, which is of interest as aberrations in neuronal lipid biochemistry have been implicated in AD pathogenesis. Discussion: In this study, we introduce the methodological concepts and challenges of MALDI-MSI for the studies of AD pathogenesis. Diverse Aβ isoforms including various C- and N-terminal truncations in AD and CAA brain tissues will be visualized. Despite the close relationship between vascular and plaque Aβ deposition, the current strategy will define cross talk between neurodegenerative and cerebrovascular processes at the level of Aβ metabolism.