Cellular localization of p-tau217 in brain and its association with p-tau217 plasma levels

Recent studies highlight phosphorylated tau (p-tau) at threonine tau 217 (p-tau217) as a new promising plasma biomarker for pathological changes implicated in Alzheimer’s disease (AD), but the specific brain pathological events related to the alteration in p-tau217 plasma levels are still largely unknown. Using immunostaining techniques of postmortem AD brain tissue, we show that p-tau217 is found in neurofibrillary tangles (NFTs) and neuropil threads that are also positive for p-tau181, 202, 202/205, 231, and 369/404. The p-tau217, but not the other five p-tau variants, was also prominently seen in vesicles structure positive for markers of granulovacuolar degeneration bodies and multi-vesicular bodies. Further, individuals with a high likelihood of AD showed significantly higher p-tau217 area fraction in 4 different brain areas (entorhinal cortex, inferior temporal gyrus, and superior frontal gyrus) compared to those with Primary age related tauopathy or other non-AD tauopathies. The p-tau217 area fraction correlated strongly with total amyloid-beta (Aβ) and NFT brain load when the whole group was analyzed. Finally, the mean p-tau217 area fraction correlated significantly with p-tau217 concentrations in antemortem collected plasma specifically in individuals with amyloid plaques and not in those without amyloid plaques. These studies highlight differences in cellular localization of different p-tau variants and suggest that plasma levels of p-tau217 reflect an accumulation of p-tau217 in presence of Aβ plaque load.

Gold nanoparticles from magnetite for the detection of amyloid proteins in neurodegenerative diseases

Introduction. Currently, neurodegenerative diseases (ND) are the fourth leading cause of death worldwide that pose a great challenge in the development of tools for early diagnosis. Thus, advances in science seek sensitive and selective detection systems and this manuscript will highlight the importance of nanotechnology. Material and methods. A literature review was conducted on the representative findings of NPs technologies in neurodegenerative diseases. Articles written in both English and Spanish were included. References between 2015-2021 were also taken into account. Results. One of the most representative techniques, AuNP was specifically implemented, together with a magnetic center composed of magnetite, which has as a specific ligand with a C-terminal cysteine domain present in the B-amyloid protein, which adhere directly to the surface of the NPs, characterizing the anomalous protein. Subsequently, by means of nanosensors capable of detecting and measuring different concentrations, these pathologies are identified at an early stage. Conclusions. Today, along with the advent of biotechnology, it has been possible to design techniques with NPs that allow the identification of specific mutations and provide diagnosis in individuals. In the investigative models of AuNP, it is possible to infer that the capabilities that make them representative focus on their magnetism and biofunctionality, by specifically binding to amyloid peptides and other ligands present in the protein, which are the major components of amyloid plaques used in these studies.

Urinary Incontinence and Alzheimer’s Disease: Insights From Patients and Preclinical Models

Alzheimer’s disease effects a large percentage of elderly dementia patients and is diagnosed on the basis of amyloid plaques and neurofibrillary tangles (NFTs) present in the brain. Urinary incontinence (UI) is often found in the elderly populations and multiple studies have shown that it is more common in Alzheimer’s disease patients than those with normal cognitive function. However, the link between increased UI and Alzheimer’s disease is still unclear. Amyloid plaques and NFTs present in micturition centers of the brain could cause a loss of signal to the bladder, resulting in the inability to properly void. Additionally, as Alzheimer’s disease progresses, patients become less likely to recognize the need or understand the appropriate time and place to void. There are several treatments for UI targeting the muscarinic and β3 adrenergic receptors, which are present in the bladder and the brain. While these treatments may aid in UI, they often have effects on the brain with cognitive impairment side-effects. Acetylcholine esterase inhibitors are often used in treatment of Alzheimer’s disease and directly oppose effects of anti-muscarinics used for UI, making UI management in Alzheimer’s disease patients difficult. There are currently over 200 pre-clinical models of Alzheimer’s disease, however, little research has been done on voiding disfunction in these models. There is preliminary data suggesting these models have similar voiding behavior to Alzheimer’s disease patients but much more research is needed to understand the link between UI and Alzheimer’s disease and discover better treatment options for managing both simultaneously.

Liraglutide Reduces Vascular Damage, Neuronal Loss, and Cognitive Impairment in a Mixed Murine Model of Alzheimer’s Disease and Type 2 Diabetes

Alzheimer’s disease is the most common form of dementia, and epidemiological studies support that type 2 diabetes (T2D) is a major contributor. The relationship between both diseases and the fact that Alzheimer’s disease (AD) does not have a successful treatment support the study on antidiabetic drugs limiting or slowing down brain complications in AD. Among these, liraglutide (LRGT), a glucagon-like peptide-1 agonist, is currently being tested in patients with AD in the Evaluating Liraglutide in Alzheimer’s Disease (ELAD) clinical trial. However, the effects of LRGT on brain pathology when AD and T2D coexist have not been assessed. We have administered LRGT (500 μg/kg/day) to a mixed murine model of AD and T2D (APP/PS1xdb/db mice) for 20 weeks. We have evaluated metabolic parameters as well as the effects of LRGT on learning and memory. Postmortem analysis included assessment of brain amyloid-β and tau pathologies, microglia activation, spontaneous bleeding and neuronal loss, as well as insulin and insulin-like growth factor 1 receptors. LRGT treatment reduced glucose levels in diabetic mice (db/db and APP/PS1xdb/db) after 4 weeks of treatment. LRGT also helped to maintain insulin levels after 8 weeks of treatment. While we did not detect any effects on cortical insulin or insulin-like growth factor 1 receptor m-RNA levels, LRGT significantly reduced brain atrophy in the db/db and APP/PS1xdb/db mice. LRGT treatment also rescued neuron density in the APP/PS1xdb/db mice in the proximity (p = 0.008) far from amyloid plaques (p < 0.001). LRGT reduced amyloid plaque burden in the APP/PS1 animals (p < 0.001), as well as Aβ aggregates levels (p = 0.046), and tau hyperphosphorylation (p = 0.009) in the APP/PS1xdb/db mice. Spontaneous bleeding was also ameliorated in the APP/PS1xdb/db animals (p = 0.012), and microglia burden was reduced in the proximity of amyloid plaques in the APP/PS1 and APP/PS1xdb/db mice (p < 0.001), while microglia was reduced in areas far from amyloid plaques in the db/db and APP/PS1xdb/db mice (p < 0.001). This overall improvement helped to rescue cognitive impairment in AD-T2D mice in the new object discrimination test (p < 0.001) and Morris water maze (p < 0.001). Altogether, our data support the role of LRGT in reduction of associated brain complications when T2D and AD occur simultaneously, as regularly observed in the clinical arena.

Validation of Plasma Amyloid-β 42/40 for Detecting Alzheimer Disease Amyloid Plaques

Objective:To determine the diagnostic accuracy of a plasma Aβ42/Aβ40 assay in classifying amyloid PET status across global research studies using samples collected by multiple centers that utilize different blood collection and processing protocols.Methods:Plasma samples (n=465) were obtained from three large Alzheimer’s Disease (AD) research cohorts in the US (n=182), Australia (n=183), and Sweden (n=100). Plasma Aβ42/Aβ40 was measured by a high precision immunoprecipitation mass spectrometry (IPMS) assay and compared to the reference standards of amyloid PET and CSF Aβ42/Aβ40.Results:In the combined cohort of 465 participants, plasma Aβ42/Aβ40 had good concordance with amyloid PET status (Receiver Operating Characteristic Area Under the Curve [AUC] of 0.84, 95% confidence interval [CI] 0.80-0.87); concordance improved with the inclusion of APOE ε4 status (AUC 0.88, 95% CI 0.85-0.91). The AUC of plasma Aβ42/Aβ40 with CSF amyloid status was 0.85 (95% CI 0.78-0.91) and improved to 0.93 (95% CI 0.89-0.97) with APOE ε4 status. These findings were consistent across the three cohorts, despite differences in protocols. Further, the assay performed similarly in both cognitively unimpaired and impaired individuals.Conclusions:Plasma Aβ42/Aβ40 is a robust measure for detecting amyloid plaques and can be utilized to aid in the diagnosis of AD, identify those at risk for future dementia due to AD, and improve the diversity of populations enrolled in AD research and clinical trials.Classification of Evidence:This study provides Class II evidence that plasma Aβ42/Aβ40, as measured by a high precision IPMS assay, accurately diagnoses brain amyloidosis in both cognitively unimpaired and impaired research participants.

Reducing voltage-dependent potassium channel Kv3.4 levels ameliorates synapse loss in a mouse model of Alzheimers disease

Synapse loss is associated with cognitive decline in Alzheimers disease (AD) and owing to their plastic nature, synapses are an ideal target for therapeutic intervention. Oligomeric amyloid beta (Ab) around amyloid plaques is known to contribute to synapse loss in mouse models and is associated with synapse loss in human AD brain tissue, but the mechanisms leading from Ab; to synapse loss remain unclear. Recent data suggest that the fast-activating and -inactivating voltage-gated potassium channel subtype 3.4 (Kv3.4) may play a role in Ab-mediated neurotoxicity. Here, we tested whether this channel could also be involved in Ab synaptotoxicity. Using adeno-associated virus and CRISPR (clustered regularly interspaced short palindromic repeats) technology, we reduced Kv3.4 expression in neurons of the somatosensory cortex of APP/PS1 mice. These mice express human familial AD associated mutations in amyloid precursor protein and presenilin 1 and develop amyloid plaques and plaque-associated synapse loss similar to that observed in AD brain. We observe that reducing Kv3.4 levels ameliorates dendritic spine loss and changes spine morphology compared to control virus. In support of translational relevance, Kv3.4 protein was observed in human AD and control brain and is associated with synapses in human iPSC-derived cortical neurons. Interestingly, we observe a decrease in Kv3.4 expression in iPSC derived cortical neurons when they are challenged with human Alzheimers disease derived brain homogenate. These results suggest that approaches to reduce Kv3.4 expression and/or function could be protective against Ab-induced synaptic alterations.

Impaired astrocytic Ca2+ signalling in awake Alzheimer's disease transgenic mice

Increased astrocytic Ca2+ signaling related to amyloid plaques has been shown in Alzheimer's disease mouse models, but to date no reports have characterized behaviorally induced astrocytic Ca2+ signalling in such mice without the confounding effects of anesthesia. Here, we employ an event-based algorithm to assess astrocytic Ca2+ signals in the neocortex of awake-behaving tg-ArcSwe mice and non-transgenic wildtype littermates while monitoring pupil responses and behavior. We demonstrate an attenuated astrocytic Ca2+ response to locomotion and an uncoupling of pupil responses and astrocytic Ca2+ signalling in 15-months old plaque-bearing mice. This points to a potential decoupling of neuromodulatory activation and astrocytic Ca2+ activity, which may account for some of the cognitive dysfunctions observed in Alzheimer’s disease.

Neuropathological Changes in the Brains of Suicide Killers

Background: Homicide combined with subsequent suicide of the perpetrator is a particular form of interpersonal violence and, at the same time, a manifestation of extreme aggression directed against oneself. Despite the relatively well-described individual acts of homicide and suicide, both in terms of psychopathology and law, acts of homicide and subsequent suicide committed by the same person are not well-studied phenomena. The importance of emotional factors, including the influence of mental state deviations (psychopathology), on this phenomenon, is discussed in the literature, but still there is relatively little data with which to attempt neuropathological assessments of the brains of suicide killers. This paper is dedicated to the issue based on the neuropathological studies performed. Methods: We analyzed a group of murder–suicides using histochemical and immunohistochemical methods. Results: The results of our research indicate the presence of neurodegenerative changes including multiple deposits of ß-amyloid in the form of senile/amyloid plaques and perivascular diffuse plaques. Conclusions: Neurodegenerative changes found in the analyzed brains of suicide killers may provide an interesting starting point for a number of analyses. The presence of neurodegenerative changes at such a young age in some murderers may suggest preclinical lesions that affect cognitive functions and are associated with depressed moods.

Concerted cellular responses to type I interferon propel memory impairment associated with amyloid β plaques

Despite well-documented maladaptive neuroinflammation in Alzheimer's disease (AD), the principal signal that drives memory and cognitive impairment remains elusive. Here, we reveal robust, age-dependent cellular reactions to type I interferon (IFN), an innate immune cytokine aberrantly elicited by beta-amyloid plaques, and examine their role in cognition and neuropathology relevant to AD in a murine amyloidosis model. Long-term blockade of IFN receptor rescued both memory and synaptic deficits and resulted in reduced microgliosis, inflammation, and neuritic pathology. Interestingly, microglia-specific IFN receptor ablation attenuated the loss of post-synaptic terminals, whereas IFN signaling in neural cells contributed to pre-synaptic alteration and plaque accumulation. Intriguingly, IFN pathway activation displayed a strong inverse correlation with cognitive performance, promoting selective synapse engulfment by microglia rather than amyloid plaques. Overall, IFN signaling represents a critical module within the neuroinflammatory network of AD and prompts a concerted cellular state that is detrimental to memory and cognition.