Diagnosing Alzheimer’s Disease from Circulating Blood Leukocytes Using a Fluorescent Amyloid Probe

Background: Toxic amyloid-β (Aβ) peptides aggregate into higher molecular weight assemblies and accumulate not only in the extracellular space, but also in the walls of blood vessels in the brain, increasing their permeability, and promoting immune cell migration and activation. Given the prominent role of the immune system, phagocytic blood cells may contact pathological brain materials. Objective: To develop a novel method for early Alzheimer’s disease (AD) detection, we used blood leukocytes, that could act as “sentinels” after trafficking through the brain microvasculature, to detect pathological amyloid by labelling with a conformationally-sensitive fluorescent amyloid probe and imaging with confocal spectral microscopy. Methods: Formalin-fixed peripheral blood mononuclear cells (PBMCs) from cognitively healthy control (HC) subjects, mild cognitive impairment (MCI) and AD patients were stained with the fluorescent amyloid probe K114, and imaged. Results were validated against cerebrospinal fluid (CSF) biomarkers and clinical diagnosis. Results: K114-labeled leukocytes exhibited distinctive fluorescent spectral signatures in MCI/AD subjects. Comparing subjects with single CSF biomarker-positive AD/MCI to negative controls, our technique yielded modest AUCs, which improved to the 0.90 range when only MCI subjects were included in order to measure performance in an early disease state. Combining CSF Aβ 42 and t-Tau metrics further improved the AUC to 0.93. Conclusion: Our method holds promise for sensitive detection of AD-related protein misfolding in circulating leukocytes, particularly in the early stages of disease.

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In Vivo Microdialysis in Mice Captures Changes in Alzheimer’s Disease Cerebrospinal Fluid Biomarkers Consistent with Developing Pathology

Journal of Alzheimer s Disease ◽

10.3233/jad-210715 ◽

2021 ◽

pp. 1-14

Author(s):

Christiana Bjorkli ◽

Claire Louet ◽

Trude Helen Flo ◽

Mary Hemler ◽

Axel Sandvig ◽

...

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Cerebrospinal Fluid ◽

Mouse Model ◽

Amyloid Β ◽

Csf Biomarkers ◽

Intracerebral Microdialysis ◽

Preclinical Models ◽

The Brain

Background: Preclinical models of Alzheimer’s disease (AD) can provide valuable insights into the onset and progression of the disease, such as changes in concentrations of amyloid-β (Aβ) and tau in cerebrospinal fluid (CSF). However, such models are currently underutilized due to limited advancement in techniques that allow for longitudinal CSF monitoring. Objective: An elegant way to understand the biochemical environment in the diseased brain is intracerebral microdialysis, a method that has until now been limited to short-term observations, or snapshots, of the brain microenvironment. Here we draw upon patient-based findings to characterize CSF biomarkers in a commonly used preclinical mouse model for AD. Methods: Our modified push-pull microdialysis method was first validated ex vivo with human CSF samples, and then in vivo in an AD mouse model, permitting assessment of dynamic changes of CSF Aβ and tau and allowing for better translational understanding of CSF biomarkers. Results: We demonstrate that CSF biomarker changes in preclinical models capture what is observed in the brain; with a decrease in CSF Aβ observed when plaques are deposited, and an increase in CSF tau once tau pathology is present in the brain parenchyma. We found that a high molecular weight cut-off membrane allowed for simultaneous sampling of Aβ and tau, comparable to CSF collection by lumbar puncture in patients. Conclusion: Our approach can further advance AD and other neurodegenerative research by following evolving neuropathology along the disease cascade via consecutive sampling from the same animal and can additionally be used to administer pharmaceutical compounds and assess their efficacy (Bjorkli, unpublished data).

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Identifying the Main Functional Pathways Associated with Cognitive Resilience to Alzheimer’s Disease

International Journal of Molecular Sciences ◽

10.3390/ijms22179120 ◽

2021 ◽

Vol 22 (17) ◽

pp. 9120

Author(s):

Marta Pérez-González ◽

Sara Badesso ◽

Elena Lorenzo ◽

Elizabeth Guruceaga ◽

Alberto Pérez-Mediavilla ◽

...

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Mononuclear Cells ◽

Memory Function ◽

Temporal Cortex ◽

Mrna Levels ◽

Peripheral Blood Mononuclear ◽

Novel Treatments ◽

Peripheral Immune Cells ◽

The Brain

Understanding the mechanisms involved in cognitive resilience in Alzheimer’s disease (AD) represents a promising strategy to identify novel treatments for dementia in AD. Previous findings from our group revealed that the study of aged-Tg2576 cognitive resilient individuals is a suitable tool for this purpose. In the present study, we performed a transcriptomic analysis using the prefrontal cortex of demented and resilient Tg2576 transgenic AD mice. We have been able to hypothesize that pathways involved in inflammation, amyloid degradation, memory function, and neurotransmission may be playing a role on cognitive resilience in AD. Intriguingly, the results obtained in this study are suggestive of a reduction of the influx of peripheral immune cells into the brain on cognitive resilient subjects. Indeed, Cd4 mRNA expression is significantly reduced on Tg2576 mice with cognitive resilience. For further validation of this result, we analyzed CD4 expression in human AD samples, including temporal cortex and peripheral blood mononuclear cells (PBMC). Interestingly, we have found a negative correlation between CD4 mRNA levels in the periphery and the score in the Mini-Mental State Exam of AD patients. These findings highlight the importance of understanding the role of the immune system on the development of neurodegenerative diseases and points out to the infiltration of CD4+ cells in the brain as a key player of cognitive dysfunction in AD.

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Tapping Into the Aging Brain: in Vivo Microdialysis Reveals Mirroring Pathology Between Preclinical Models and Patients With Alzheimer’s Disease

10.21203/rs.3.rs-204241/v1 ◽

2021 ◽

Author(s):

Christiana Bjorkli ◽

Claire Louet ◽

Trude Helen Flo ◽

Mary Hemler ◽

Axel Sandvig ◽

...

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Amyloid Β ◽

In Vivo Microdialysis ◽

Optimal Recovery ◽

Aging Brain ◽

Csf Biomarkers ◽

Intracerebral Microdialysis ◽

The Brain

Abstract BackgroundPreclinical models of Alzheimer’s disease (AD) can provide valuable insights into the onset and progression of the disease, such as changes in concentrations of amyloid-β (Aβ) and tau in cerebrospinal fluid (CSF). However, such models are currently underutilized due to limited advancement in techniques that allow for longitudinal monitoring of CSF akin to methods employed in AD patients. An elegant way to understand the biochemical environment in the diseased brain is intracerebral microdialysis, a method that has until now been limited to short-term observations, or snapshots, of the brain microenvironment. ResultsOur novel push-pull microdialysis method in AD mice permits in vivo longitudinal monitoring of dynamic changes of Aβ and tau in CSF and allows for better translational understanding of CSF biomarkers. Specifically, we demonstrate that CSF concentrations of Aβ and tau along disease progression in transgenic mice mirror what is observed in patients, with a decrease in CSF Aβ observed when plaques are deposited, and an increase in CSF tau once tau pathology is present in the brain. We found that a high molecular weight cut-off membrane allowed for simultaneous sampling of Aβ and tau, comparable to lumbar puncture CSF collection in patients. We furthermore provide specific recommendations for optimal application of our novel microdialysis method, such as achieving optimal recovery of analytes, which depends heavily on the flow rate of perfusion, probe properties and perfusate composition. ConclusionsOur approach can further advance AD research by following evolving neuropathology along the disease cascade via consecutive sampling from the same animal, and can additionally be used to administer pharmaceutical compounds and assess their efficacy in treating AD.

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Bacterial Extracellular DNA Promotes β-Amyloid Aggregation

Microorganisms ◽

10.3390/microorganisms9061301 ◽

2021 ◽

Vol 9 (6) ◽

pp. 1301

Author(s):

George Tetz ◽

Victor Tetz

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Protein Misfolding ◽

Amyloid Β ◽

Extracellular Dna ◽

Bacterial Dna ◽

Aβ Aggregation ◽

The Brain

Alzheimer’s disease is associated with prion-like aggregation of the amyloid β (Aβ) peptide and the subsequent accumulation of misfolded neurotoxic aggregates in the brain. Therefore, it is critical to clearly identify the factors that trigger the cascade of Aβ misfolding and aggregation. Numerous studies have pointed out the association between microorganisms and their virulence factors and Alzheimer’s disease; however, their exact mechanisms of action remain unclear. Recently, we discovered a new pathogenic role of bacterial extracellular DNA, triggering the formation of misfolded Tau aggregates. In this study, we investigated the possible role of DNA extracted from different bacterial and eukaryotic cells in triggering Aβ aggregation in vitro. Interestingly, we found that the extracellular DNA of some, but not all, bacteria is an effective trigger of Aβ aggregation. Furthermore, the acceleration of Aβ nucleation and elongation can vary based on the concentration of the bacterial DNA and the bacterial strain from which this DNA had originated. Our findings suggest that bacterial extracellular DNA might play a previously overlooked role in the Aβ protein misfolding associated with Alzheimer’s disease pathogenesis. Moreover, it highlights a new mechanism of how distantly localized bacteria can remotely contribute to protein misfolding and diseases associated with this process. These findings might lead to the use of bacterial DNA as a novel therapeutic target for the prevention and treatment of Alzheimer’s disease.

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Low-grade peripheral inflammation affects brain pathology in the AppNL-G-Fmouse model of Alzheimer’s disease

Acta Neuropathologica Communications ◽

10.1186/s40478-021-01253-z ◽

2021 ◽

Vol 9 (1) ◽

Author(s):

Junhua Xie ◽

Nina Gorlé ◽

Charysse Vandendriessche ◽

Griet Van Imschoot ◽

Elien Van Wonterghem ◽

...

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Microglial Activation ◽

Immune Cell ◽

Amyloid Β ◽

Peripheral Inflammation ◽

Low Grade ◽

Model Of Alzheimer’S Disease ◽

Aβ Aggregation ◽

The Brain

AbstractAlzheimer’s disease (AD) is a chronic neurodegenerative disease characterized by the accumulation of amyloid β (Aβ) and neurofibrillary tangles. The last decade, it became increasingly clear that neuroinflammation plays a key role in both the initiation and progression of AD. Moreover, also the presence of peripheral inflammation has been extensively documented. However, it is still ambiguous whether this observed inflammation is cause or consequence of AD pathogenesis. Recently, this has been studied using amyloid precursor protein (APP) overexpression mouse models of AD. However, the findings might be confounded by APP-overexpression artifacts. Here, we investigated the effect of low-grade peripheral inflammation in the APP knock-in (AppNL-G-F) mouse model. This revealed that low-grade peripheral inflammation affects (1) microglia characteristics, (2) blood-cerebrospinal fluid barrier integrity, (3) peripheral immune cell infiltration and (4) Aβ deposition in the brain. Next, we identified mechanisms that might cause this effect on AD pathology, more precisely Aβ efflux, persistent microglial activation and insufficient Aβ clearance, neuronal dysfunction and promotion of Aβ aggregation. Our results further strengthen the believe that even low-grade peripheral inflammation has detrimental effects on AD progression and may further reinforce the idea to modulate peripheral inflammation as a therapeutic strategy for AD.

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microRNA-150-5p: A Novel Blood-Based Biomarker for Alzheimer’s Dementia with Good Correlation to Cognition, Cerebrospinal Fluid Amyloid-β, and Cerebral Atrophy

10.21203/rs.3.rs-942370/v1 ◽

2021 ◽

Author(s):

Sook-Yoong Chia ◽

Ashwati Vipin ◽

Kok-Pin Ng ◽

Haitao Tu ◽

Ananth Bommakanti ◽

...

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Medial Temporal Lobe ◽

Target Genes ◽

Mononuclear Cells ◽

Amyloid Β ◽

Cerebral Atrophy ◽

Posterior Cingulate Cortex ◽

Peripheral Blood Mononuclear ◽

Clinical Measures

Abstract Background: There is an urgent need for non-invasive, cost-effective biomarkers for Alzheimer’s disease (AD), such as blood-based biomarkers. It is not only to support clinical diagnosis of dementia, but also to allow for timely pharmacological and non-pharmacological interventions evaluation. The aim of this study is to identify and validate a novel blood-based microRNA (miRNA) biomarker for dementia of Alzheimer’s disease type (DAT). The miRNA correlations with AD pathology and AD clinical-radiological imaging were conducted.Methods: We conducted miRNA-sequencing (miRNA-Seq) using peripheral blood mononuclear cells (PBMCs) isolated from a discovery cohort comprising DAT, mild cognitive impairment (MCI), and healthy subject (HS). Identified miRNA was validated in an independent cohort. Correlation analysis evaluated the relationships between miRNA expression and DAT clinical measures, including Mini-Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA) scores, CSF Aβ1-42 and tau levels, and AD pattern cerebral atrophy. Furthermore, we conducted bioinformatics analysis and cell-based assay to identify miRNA target genes. Results: MiRNA-seq identified a distinct miRNA (miR-328-3p, miR-7706, and miR-150-5p) expression signature differentiating DAT from MCI and HS. qPCR analysis reveals that miR-150-5p was consistent with the miRNA-seq data and was further validated. Specifically, we found that miR-150-5p expression was significantly upregulated in DAT compared to MCI and HS, and discriminated DAT from MCI and HS with a high accuracy with AUC of 0.86 and 0.86, respectively. We further found that higher miR-150-5p levels correlated with clinical measures of DAT, including lower global cognitive scores of MMSE and MoCA, lower CSF Aβ1-42, and higher CSF tau. Interestingly, we observed that higher miR-150-5p levels is associated with the lower grey matter volumes in the medial temporal lobe, posterior cingulate cortex and precuneus. These regions implicated default mood network and executive control network regions that are important for AD brain atrophy. Furthermore, pathway analysis identified the targets of miR-150-5p to be enriched in the Wnt signalling pathway, including programmed cell death 4 (PDCD4). We further found that PDCD4 was downregulated in DAT blood and was downregulated by miR-150-5p at both transcriptional and protein levels.Conclusions: Our findings demonstrated that miR-150-5p is a reliable clinical blood-based biomarker for DAT.

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Tapping into the aging brain: In vivo microdialysis reveals mirroring pathology between preclinical models and patients with Alzheimer’s disease

10.1101/2021.01.23.427888 ◽

2021 ◽

Author(s):

C. Bjorkli ◽

C. Louet ◽

T.H. Flo ◽

M. Hemler ◽

A. Sandvig ◽

...

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Amyloid Β ◽

In Vivo Microdialysis ◽

Aging Brain ◽

Csf Biomarkers ◽

Intracerebral Microdialysis ◽

Preclinical Models ◽

The Brain

SUMMARYPreclinical models of Alzheimer’s disease (AD) can provide valuable insights into the onset and progression of the disease, such as changes in concentrations of amyloid-β (Aβ) and tau in cerebrospinal fluid (CSF). However, such models are currently underutilized due to limited advancement in techniques that allow for longitudinal monitoring of CSF akin to methods employed in AD patients. An elegant way to understand the biochemical environment in the diseased brain is intracerebral microdialysis, a method that has until now been limited to short-term observations, or snapshots, of the brain microenvironment. Our novel push-pull microdialysis method in AD mice permits in vivo longitudinal monitoring of dynamic changes of Aβ and tau in CSF and allows for better translational understanding of CSF biomarkers. Specifically, we demonstrate that CSF concentrations of Aβ and tau along disease progression in transgenic mice mirror what is observed in patients, with a decrease in CSF Aβ observed when plaques are deposited, and an increase in CSF tau once tau pathology is present in the brain. We found that a high molecular weight cut-off membrane allowed for simultaneous sampling of Aβ and tau, comparable to lumbar puncture CSF collection in patients. We furthermore provide specific recommendations for optimal application of our novel microdialysis method, such as achieving optimal recovery of analytes, which depends heavily on the flow rate of perfusion, probe properties and perfusate composition. Our approach can further advance AD research by following evolving neuropathology along the disease cascade via consecutive sampling from the same animal, and can additionally be used to administer pharmaceutical compounds and assess their efficacy in treating AD.

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Peripheral Markers of Vascular Endothelial Dysfunction Show Independent but Additive Relationships with Brain-Based Biomarkers in Association with Functional Impairment in Alzheimer’s Disease

Journal of Alzheimer s Disease ◽

10.3233/jad-200759 ◽

2021 ◽

pp. 1-13

Author(s):

Jonathan D. Drake ◽

Alison B. Chambers ◽

Brian R. Ott ◽

Lori A. Daiello ◽

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Cell Adhesion ◽

Adhesion Molecule ◽

Functional Impairment ◽

Amyloid Β ◽

Intercellular Adhesion Molecule ◽

Csf Biomarkers ◽

Linear Regression Models ◽

Cognitively Normal

Background: Cerebrovascular dysfunction confers risk for functional decline in Alzheimer’s disease (AD), yet the clinical interplay of these two pathogenic processes is not well understood. Objective: We utilized Alzheimer’s Disease Neuroimaging Initiative (ADNI) data to examine associations between peripherally derived soluble cell adhesion molecules (CAMs) and clinical diagnostic indicators of AD. Methods: Using generalized linear regression models, we examined cross-sectional relationships of soluble plasma vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1), and E-Selectin to baseline diagnosis and functional impairment (clinical dementia rating sum-of-boxes, CDR-SB) in the ADNI cohort (n = 112 AD, n = 396 mild cognitive impairment (MCI), n = 58 cognitively normal). We further analyzed associations of these biomarkers with brain-based AD biomarkers in a subset with available cerebrospinal fluid (CSF) data (n = 351). p-values derived from main effects and interaction terms from the linear regressions were used to assess the relationship between independent and dependent variables for significance (significance level was set at 0.05 a priori for all analysis). Results: Higher mean VCAM-1 (p = 0.0026) and ICAM-1 (p = 0.0189) levels were found in AD versus MCI groups; however, not in MCI versus cognitively normal groups. Only VCAM-1 was linked with CDR-SB scores (p = 0.0157), and APOE ɛ4 genotype modified this effect. We observed independent, additive associations when VCAM-1 and CSF amyloid-β (Aβ 42), total tau, phosphorylated tau (P-tau), or P-tau/Aβ 42 (all < p = 0.01) were combined in a CDR-SB model; ICAM-1 showed a similar pattern, but to a lesser extent. Conclusion: Our findings indicate independent associations of plasma-based vascular biomarkers and CSF biomarkers with AD-related clinical impairment.

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Oral Amylin Treatment Reduces the Pathological Cascade of Alzheimer’s Disease in a Mouse Model

American Journal of Alzheimer s Disease & Other Dementias® ◽

10.1177/15333175211012867 ◽

2021 ◽

Vol 36 ◽

pp. 153331752110128

Author(s):

Hana Na ◽

Hua Tian ◽

Zhengrong Zhang ◽

Qiang Li ◽

Jack B. Yang ◽

...

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Calcium Binding ◽

Oral Delivery ◽

Amyloid Β ◽

Enteric Neurons ◽

Cyclin Dependent Kinase ◽

Receptor Activity Modifying Proteins ◽

The Brain ◽

Cyclin Dependent Kinase 5

Intraperitoneal injection of amylin or its analog reduces Alzheimer’s disease (AD) pathology in the brains. However, self-injecting amylin analogs is difficult for patients due to cognitive deficits. This work aims to study the effects of amylin on the brain could be achieved by oral delivery as some study reported that amylin receptor may be present in the gastrointestinal tract. A 6-week course of oral amylin treatment reduced components of AD pathology, including the levels of amyloid-β, phosphorylated tau, and ionized calcium binding adaptor molecule 1. The treatment reduced active forms of cyclin-dependent kinase 5. Oral amylin treatment led to improvements in social deficit in AD mouse. Using immunofluorescence, we observed the amylin receptor complexed with the calcitonin receptor and receptor activity-modifying proteins in the enteric neurons. The study suggests the potential of the oral delivery of amylin analogs for the treatment of AD and other neurodegenerative diseases through enteric neurons.

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Identification of Novel Cathepsin B Inhibitors with Implications in Alzheimer’s Disease: Computational Refining and Biochemical Evaluation

Cells ◽

10.3390/cells10081946 ◽

2021 ◽

Vol 10 (8) ◽

pp. 1946

Author(s):

Nitin Chitranshi ◽

Ashutosh Kumar ◽

Samran Sheriff ◽

Veer Gupta ◽

Angela Godinez ◽

...

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Hydrogen Bond ◽

Virtual Screening ◽

Cathepsin B ◽

Amyloid Β ◽

Proteolytic Degradation ◽

Hydrogen Bond Acceptor ◽

Starting Point ◽

The Brain

Amyloid precursor protein (APP), upon proteolytic degradation, forms aggregates of amyloid β (Aβ) and plaques in the brain, which are pathological hallmarks of Alzheimer’s disease (AD). Cathepsin B is a cysteine protease enzyme that catalyzes the proteolytic degradation of APP in the brain. Thus, cathepsin B inhibition is a crucial therapeutic aspect for the discovery of new anti-Alzheimer’s drugs. In this study, we have employed mixed-feature ligand-based virtual screening (LBVS) by integrating pharmacophore mapping, docking, and molecular dynamics to detect small, potent molecules that act as cathepsin B inhibitors. The LBVS model was generated by using hydrophobic (HY), hydrogen bond acceptor (HBA), and hydrogen bond donor (HBD) features, using a dataset of 24 known cathepsin B inhibitors of both natural and synthetic origins. A validated eight-feature pharmacophore hypothesis (Hypo III) was utilized to screen the Maybridge chemical database. The docking score, MM-PBSA, and MM-GBSA methodology was applied to prioritize the lead compounds as virtual screening hits. These compounds share a common amide scaffold, and showed important interactions with Gln23, Cys29, His110, His111, Glu122, His199, and Trp221. The identified inhibitors were further evaluated for cathepsin-B-inhibitory activity. Our study suggests that pyridine, acetamide, and benzohydrazide compounds could be used as a starting point for the development of novel therapeutics.

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