Dysregulated Gut Homeostasis Observed Prior to the Accumulation of the Brain Amyloid-β in Tg2576 Mice

Amyloid plaques in Alzheimer’s disease (AD) are associated with inflammation. Recent studies demonstrated the involvement of the gut in cerebral amyloid-beta (Aβ) pathogenesis; however, the mechanisms are still not well understood. We hypothesize that the gut bears the Aβ burden prior to brain, highlighting gut–brain axis (GBA) interaction in neurodegenerative disorders. We used pre-symptomatic (6-months) and symptomatic (15-months) Tg2576 mouse model of AD compared to their age-matched littermate WT control. We identified that dysfunction of intestinal epithelial barrier (IEB), dysregulation of absorption, and vascular Aβ deposition in the IEB occur before cerebral Aβ aggregation is detectible. These changes in the GBA were associated with elevated inflammatory plasma cytokines including IL-9, VEGF and IP-10. In association with reduced cerebral myelin tight junction proteins, we identified reduced levels of systemic vitamin B12 and decrease cubilin, an intestinal B12 transporter, after the development of cerebral Aβ pathology. Lastly, we report Aβ deposition in the intestinal autopsy from AD patients with confirmed cerebral Aβ pathology that is not present in intestine from non-AD controls. Our data provide evidence that gut dysfunction occurs in AD and may contribute to its etiology. Future therapeutic strategies to reverse AD pathology may involve the early manipulation of gut physiology and its microbiota.

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The Clustering of mApoE Anti-Amyloidogenic Peptide on Nanoparticle Surface Does Not Alter Its Performance in Controlling Beta-Amyloid Aggregation

International Journal of Molecular Sciences ◽

10.3390/ijms21031066 ◽

2020 ◽

Vol 21 (3) ◽

pp. 1066

Author(s):

Roberta Corti ◽

Alysia Cox ◽

Valeria Cassina ◽

Luca Nardo ◽

Domenico Salerno ◽

...

Keyword(s):

Amyloid Β ◽

Force Microscopy ◽

Atomic Force ◽

Nanoparticle Surface ◽

Afm Imaging ◽

Aggregation Processes ◽

Aβ Aggregation ◽

Aβ Fibrils ◽

Binding Sequence ◽

The Brain

The deposition of amyloid-β (Aβ) plaques in the brain is a significant pathological signature of Alzheimer’s disease, correlating with synaptic dysfunction and neurodegeneration. Several compounds, peptides, or drugs have been designed to redirect or stop Aβ aggregation. Among them, the trideca-peptide CWG-LRKLRKRLLR (mApoE), which is derived from the receptor binding sequence of apolipoprotein E, is effectively able to inhibit Aβ aggregation and to promote fibril disaggregation. Taking advantage of Atomic Force Microscopy (AFM) imaging and fluorescence techniques, we investigate if the clustering of mApoE on gold nanoparticles (AuNP) surface may affect its performance in controlling Aβ aggregation/disaggregation processes. The results showed that the ability of free mApoE to destroy preformed Aβ fibrils or to hinder the Aβ aggregation process is preserved after its clustering on AuNP. This allows the possibility to design multifunctional drug delivery systems with clustering of anti-amyloidogenic molecules on any NP surface without affecting their performance in controlling Aβ aggregation processes.

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How Do the Size, Charge and Shape of Nanoparticles Affect Amyloid β Aggregation on Brain Lipid Bilayer?

Scientific Reports ◽

10.1038/srep19548 ◽

2016 ◽

Vol 6 (1) ◽

Cited By ~ 51

Author(s):

Yuna Kim ◽

Ji-Hyun Park ◽

Hyojin Lee ◽

Jwa-Min Nam

Keyword(s):

Lipid Bilayer ◽

Neuroblastoma Cells ◽

Amyloid Β ◽

Random Coil ◽

Brain Lipid ◽

Nanoparticle Shape ◽

Total Brain ◽

Aβ Aggregation ◽

Shape Of Nanoparticles ◽

The Brain

Abstract Here, we studied the effect of the size, shape and surface charge of Au nanoparticles (AuNPs) on amyloid beta (Aβ) aggregation on a total brain lipid-based supported lipid bilayer (brain SLB), a fluid platform that facilitates Aβ-AuNP aggregation process. We found that larger AuNPs induce large and amorphous aggregates on the brain SLB, whereas smaller AuNPs induce protofibrillar Aβ structures. Positively charged AuNPs were more strongly attracted to Aβ than negatively charged AuNPs and the stronger interactions between AuNPs and Aβ resulted in fewer β-sheets and more random coil structures. We also compared spherical AuNPs, gold nanorods (AuNRs) and gold nanocubes (AuNCs) to study the effect of nanoparticle shape on Aβ aggregation on the brain SLB. Aβ was preferentially bound to the long axis of AuNRs and fewer fibrils were formed whereas all the facets of AuNCs interacted with Aβ to produce the fibril networks. Finally, it was revealed that different nanostructures induce different cytotoxicity on neuroblastoma cells, and, overall, smaller Aβ aggregates induce higher cytotoxicity. The results offer insight into the roles of NPs and brain SLB in Aβ aggregation on the cell membrane and can facilitate the understanding of Aβ-nanostructure co-aggregation mechanism and tuning Aβ aggregate structures.

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MTOR PROMOTES BBB BREAKDOWN IN A MODEL OF ALZHEIMER’S DISEASE

Innovation in Aging ◽

10.1093/geroni/igz038.957 ◽

2019 ◽

Vol 3 (Supplement_1) ◽

pp. S256-S256 ◽

Cited By ~ 1

Author(s):

Stephen F Hernandez ◽

Candice E Van Skike ◽

Nick DeRosa ◽

Veronica Galvan

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Mouse Model ◽

Tight Junction ◽

Tg2576 Mouse ◽

Tight Junction Proteins ◽

Study Results ◽

Junction Protein ◽

Tg2576 Mice ◽

Junction Proteins

Abstract Cerebral amyloid angiopathy (CAA) is characterized by fibrillar amyloid β (Aβ) association with cerebrovasculature, which leads to impaired brain vascular function, and is present in 87% of people with Alzheimer’s disease (AD). We previously showed that inhibition of mTOR by rapamycin prevented BBB breakdown and reduced vascular fibrillar Aβ in 18-19 month old Tg2576 mice that model AD-associated CAA. This finding suggests that mTOR attenuation restores integrity of the blood brain barrier (BBB) and concomitantly reduces vascular Aβ accumulation in this mouse model. Objective: To determine the mechanisms by which mTOR drives BBB breakdown we measured the abundance of tight junction proteins zonula occludens 1 (ZO-1), occludin, and claudin-5. Methods: We used immunofluorescent confocal microscopy on frozen brain tissue sections of the same Tg2576 mice used in the previous study. Results: We confirm BBB breakdown in Tg2576 mouse brains and showed that some, but not all tight junction proteins measured were decreased in cerebrovasculature of Tg2576 mice. Attenuation of mTOR by rapamycin preserved BBB integrity, decreased vascular Aβ accumulation, and increased levels of tight junction protein abundance in Tg2576 mice, which also showed a reduced numbers of cerebral microhemorrhages. Conclusions: Taken together, these data suggest that mTOR promotes brain vascular Aβ deposition, BBB breakdown and vascular damage in the Tg2576 mouse model. Thus, mTOR inhibitors such as rapamycin – an FDA approved drug - may have promise in the treatment of AD and other dementias with related cerebrovascular dysfunction.

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TLR2 and TLR4 in Parkinson’s disease pathogenesis: the environment takes a toll on the gut

Translational Neurodegeneration ◽

10.1186/s40035-021-00271-0 ◽

2021 ◽

Vol 10 (1) ◽

Author(s):

Anastazja M. Gorecki ◽

Chidozie C. Anyaegbu ◽

Ryan S. Anderton

Keyword(s):

Parkinson’S Disease ◽

Parkinson's Disease ◽

Nervous System ◽

Intestinal Barrier ◽

The Body ◽

Enteric Neurons ◽

Gut Dysfunction ◽

Gut Homeostasis ◽

The Brain

AbstractParkinson’s disease (PD) is an incurable, devastating disorder that is characterized by pathological protein aggregation and neurodegeneration in the substantia nigra. In recent years, growing evidence has implicated the gut environment and the gut-brain axis in the pathogenesis and progression of PD, especially in a subset of people who exhibit prodromal gastrointestinal dysfunction. Specifically, perturbations of gut homeostasis are hypothesized to contribute to α-synuclein aggregation in enteric neurons, which may spread to the brain over decades and eventually result in the characteristic central nervous system manifestations of PD, including neurodegeneration and motor impairments. However, the mechanisms linking gut disturbances and α-synuclein aggregation are still unclear. A plethora of research indicates that toll-like receptors (TLRs), especially TLR2 and TLR4, are critical mediators of gut homeostasis. Alongside their established role in innate immunity throughout the body, studies are increasingly demonstrating that TLR2 and TLR4 signalling shapes the development and function of the gut and the enteric nervous system. Notably, TLR2 and TLR4 are dysregulated in patients with PD, and may thus be central to early gut dysfunction in PD. To better understand the putative contribution of intestinal TLR2 and TLR4 dysfunction to early α-synuclein aggregation and PD, we critically discuss the role of TLR2 and TLR4 in normal gut function as well as evidence for altered TLR2 and TLR4 signalling in PD, by reviewing clinical, animal model and in vitro research. Growing evidence on the immunological aetiology of α-synuclein aggregation is also discussed, with a focus on the interactions of α-synuclein with TLR2 and TLR4. We propose a conceptual model of PD pathogenesis in which microbial dysbiosis alters the permeability of the intestinal barrier as well as TLR2 and TLR4 signalling, ultimately leading to a positive feedback loop of chronic gut dysfunction promoting α-synuclein aggregation in enteric and vagal neurons. In turn, α-synuclein aggregates may then migrate to the brain via peripheral nerves, such as the vagal nerve, to contribute to neuroinflammation and neurodegeneration typically associated with PD.

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CERTL Reduces C16 Ceramide, Amyloid-β Levels and Inflammation in a Model of Alzheimer's Disease

10.21203/rs.3.rs-42740/v1 ◽

2020 ◽

Author(s):

Simone Mwenda Crivelli ◽

Qian Luo ◽

Jo Stevens ◽

Caterina Giovagnoni ◽

Daan van Kruining ◽

...

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Neuroblastoma Cells ◽

Amyloid Β ◽

Amyloid Plaque ◽

Model Of Alzheimer’S Disease ◽

Aβ Aggregation ◽

The Brain

Abstract Background: Deregulation of ceramide and sphingomyelin levels have been suggested to contribute to the pathogenesis of Alzheimer’s disease (AD). Ceramide transfer proteins (CERTs) are ceramide carriers, crucial for ceramide and sphingomyelin balance in cells. Extracellular forms of CERTs co-localize with amyloid-β (Aβ) plaques in AD brains. To date, the significance of these observations for the pathophysiology of AD remains uncertain.Methods: The plasmid expressing CERTL, the long isoform of CERTs, was used to study the interaction of CERTL with amyloid precursor protein (APP) by co-immunoprecipitation and immunofluorescence in HEK cells. The recombinant CERTL protein was employed to study interaction of CERTL with amyloid-β (Aβ), Aβ aggregation process in presence of CERTL, and the resulting changes in Aβ toxicity in neuroblastoma cells. CERTL was overexpressed in neurons by adeno associated virus (AAV) in a familial mouse model of familial AD (5xFAD). Ten weeks after transduction animal were challenged with behavior tests for memory, anxiety and locomotion. At week twelve brains were investigated for sphingolipid levels by mass spectrometry, plaques and neuroinflammation by immunohistochemistry, gene expression and/or immunoassay.Results: Here, we report that CERTL, binds to APP, modifies Aβ aggregation and reduces Aβ neurotoxicity in vitro. Furthermore, we show that intracortical injection of AAV, mediating the expression of CERTL, decreases levels of ceramide d18:1/16:0 and increases sphingomyelin levels in the brain of male transgenic mice, modelling familial AD (5xFAD). CERTL in vivo over-expression has a mild effect on animal locomotion and decreases Aβ formation and modulates microglia by decreasing their pro-inflammatory phenotype.Conclusion: Our results demonstrate a crucial role of CERTL in regulating ceramide levels in the brain, in amyloid plaque formation and neuroinflammation, thereby opening research avenues for therapeutic targets of AD and other neurodegenerative diseases.

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Eriodictyol ameliorated cognitive dysfunction in APP/PS1 mice through inhibited ferroptosis via vitamin D receptor mediated Nrf2 activation

10.21203/rs.3.rs-1046295/v1 ◽

2021 ◽

Author(s):

Lin Li ◽

Wenjun Li ◽

Xiangru Zheng ◽

Qinglong Liu ◽

Qian Du ◽

...

Keyword(s):

Vitamin D ◽

Signaling Pathway ◽

Western Blotting ◽

Vitamin D Receptor ◽

Amyloid Β ◽

Qpcr Assay ◽

Aβ Aggregation ◽

The Brain

Abstract Background Alzheimer's disease (AD) is the most common type of neurodegenerative disease in contemporary era, and it is still clinically incurable. Eriodictyol, a natural flavonoid compound mainly exists in citrus fruits and some Chinese herbal medicine, has been reported with its effect of anti-inflammatory, antioxidant, anti-cancer and neuroprotective effects. However, there are few studies on the anti-AD effect and molecular mechanism of eriodictyol. Methods APP/PS1 mice were treated with eriodictyol and the cognitive function of mice was assessed by behavioral tests. The level of amyloid-β (Aβ) aggregation and hyper-phosphorylation of Tau in the brain of mice were detected by histological analysis and Western blotting. Meanwhile, HT-22 cells which induced by amyloid-β peptide (1-42) (Aβ1−42) oligomer were treated with eriodictyol after which cell viability was determined and the production of p-Tau was tested by Western blotting. Then, the characteristics of ferroptosis, including iron aggregation, lipid peroxidation and the expression of glutathione peroxidase type 4(GPX4), were determined both in vivo and in vitro by Fe straining, Western blotting and qPCR assay. Additionally, the expression level of Vitamin D receptor (VDR) and the activity of nuclear factor erythroid 2-related factor 2/heme oxygenase-1 (Nrf2/HO-1) signaling pathway were tested by Western blotting and qPCR assay. After that, the HT-22 cells with VDR knockout were used to explore the potential mechanisms and the relationship between VDR and Nrf2 was further assessed by coimmunoprecipitation assay and bioinformatics analysis. Results Eriodictyol obviously ameliorated cognitive deficits in APP/PS1 mice, suppressed Aβ aggregation and the phosphorylated level Tau in the brain of APP/PS1 mice. Meanwhile, eriodictyol could inhibit Tau hyper-phosphorylation and neurotoxicity in HT-22 cells induced by Aβ1−42 oligomer. Furthermore, both in vivo and in vitro, eriodictyol showed the anti-ferroptosis effect and its mechanism may connected with the activation of Nrf2/HO-1 signaling pathway. Additionally, the further experiment explains that the activation of Nrf2/HO-1 signaling pathway with eriodictyol treatment mediated by VDR. Conclusions Eriodictyol alleviated memory impairment and AD-like pathological changes via activating Nrf2/HO-1 signaling pathway mediated by VDR, which provide a new possibility for the treatment of AD.

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Osmolytes: A Possible Therapeutic Molecule for Ameliorating the Neurodegeneration Caused by Protein Misfolding and Aggregation

Biomolecules ◽

10.3390/biom10010132 ◽

2020 ◽

Vol 10 (1) ◽

pp. 132 ◽

Cited By ~ 5

Author(s):

Neetu Kushwah ◽

Vishal Jain ◽

Dhananjay Yadav

Keyword(s):

Protein Misfolding ◽

Organic Molecules ◽

Pathological Condition ◽

Amyloid Β ◽

Water Molecules ◽

Amyloid Β Protein ◽

Β Protein ◽

Aβ Aggregation ◽

Protein Misfolding And Aggregation ◽

The Brain

Most of the neurological disorders in the brain are caused by the abnormal buildup of misfolded or aggregated proteins. Osmolytes are low molecular weight organic molecules usually built up in tissues at a quite high amount during stress or any pathological condition. These molecules help in providing stability to the aggregated proteins and protect these proteins from misfolding. Alzheimer’s disease (AD) is the uttermost universal neurological disorder that can be described by the deposition of neurofibrillary tangles, aggregated/misfolded protein produced by the amyloid β-protein (Aβ). Osmolytes provide stability to the folded, functional form of a protein and alter the folding balance away from aggregation and/or degradation of the protein. Moreover, they are identified as chemical chaperones. Brain osmolytes enhance the pace of Aβ aggregation, combine with the nearby water molecules more promptly, and avert the aggregation/misfolding of proteins by providing stability to them. Therefore, osmolytes can be employed as therapeutic targets and may assist in potential drug design for many neurodegenerative and other diseases.

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P4-081: Diurnal fluctuation of amyloid-β in the brain interstitial fluid of young Tg2576 mice

Alzheimer s & Dementia ◽

10.1016/j.jalz.2008.05.2146 ◽

2008 ◽

Vol 4 ◽

pp. T692-T692

Author(s):

Jae-Eun Kang ◽

John Cirrito ◽

James Lee ◽

Nobuhiro Fujiki ◽

Seiji Nishino ◽

...

Keyword(s):

Interstitial Fluid ◽

Amyloid Β ◽

Diurnal Fluctuation ◽

Brain Interstitial Fluid ◽

The Brain ◽

Tg2576 Mice

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CERTL reduces C16 ceramide, amyloid-β levels, and inflammation in a model of Alzheimer’s disease

Alzheimer s Research & Therapy ◽

10.1186/s13195-021-00780-0 ◽

2021 ◽

Vol 13 (1) ◽

Author(s):

Simone M. Crivelli ◽

Qian Luo ◽

Jo A.A. Stevens ◽

Caterina Giovagnoni ◽

Daan van Kruining ◽

...

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Neuroblastoma Cells ◽

Amyloid Β ◽

Amyloid Plaque ◽

Model Of Alzheimer’S Disease ◽

Aβ Aggregation ◽

The Brain

Abstract Background Dysregulation of ceramide and sphingomyelin levels have been suggested to contribute to the pathogenesis of Alzheimer’s disease (AD). Ceramide transfer proteins (CERTs) are ceramide carriers which are crucial for ceramide and sphingomyelin balance in cells. Extracellular forms of CERTs co-localize with amyloid-β (Aβ) plaques in AD brains. To date, the significance of these observations for the pathophysiology of AD remains uncertain. Methods A plasmid expressing CERTL, the long isoform of CERTs, was used to study the interaction of CERTL with amyloid precursor protein (APP) by co-immunoprecipitation and immunofluorescence in HEK cells. The recombinant CERTL protein was employed to study interaction of CERTL with amyloid-β (Aβ), Aβ aggregation process in presence of CERTL, and the resulting changes in Aβ toxicity in neuroblastoma cells. CERTL was overexpressed in neurons by adeno-associated virus (AAV) in a mouse model of familial AD (5xFAD). Ten weeks after transduction, animals were challenged with behavior tests for memory, anxiety, and locomotion. At week 12, brains were investigated for sphingolipid levels by mass spectrometry, plaques, and neuroinflammation by immunohistochemistry, gene expression, and/or immunoassay. Results Here, we report that CERTL binds to APP, modifies Aβ aggregation, and reduces Aβ neurotoxicity in vitro. Furthermore, we show that intracortical injection of AAV, mediating the expression of CERTL, decreases levels of ceramide d18:1/16:0 and increases sphingomyelin levels in the brain of male 5xFAD mice. CERTL in vivo over-expression has a mild effect on animal locomotion, decreases Aβ formation, and modulates microglia by decreasing their pro-inflammatory phenotype. Conclusion Our results demonstrate a crucial role of CERTL in regulating ceramide levels in the brain, in amyloid plaque formation and neuroinflammation, thereby opening research avenues for therapeutic targets of AD and other neurodegenerative diseases.

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Nanomaterials for Modulating the Aggregation of β-Amyloid Peptides

Molecules ◽

10.3390/molecules26144301 ◽

2021 ◽

Vol 26 (14) ◽

pp. 4301

Author(s):

Yaliang Huang ◽

Yong Chang ◽

Lin Liu ◽

Jianxiu Wang

Keyword(s):

Synergistic Effects ◽

Amyloid Β ◽

Therapeutic Agents ◽

Aβ Peptides ◽

Amyloid Peptides ◽

Prevention And Treatment ◽

Aβ Aggregation ◽

Β Amyloid ◽

The Brain ◽

Insight Into

The aberrant aggregation of amyloid-β (Aβ) peptides in the brain has been recognized as the major hallmark of Alzheimer’s disease (AD). Thus, the inhibition and dissociation of Aβ aggregation are believed to be effective therapeutic strategiesforthe prevention and treatment of AD. When integrated with traditional agents and biomolecules, nanomaterials can overcome their intrinsic shortcomings and boost their efficiency via synergistic effects. This article provides an overview of recent efforts to utilize nanomaterials with superior properties to propose effective platforms for AD treatment. The underlying mechanismsthat are involved in modulating Aβ aggregation are discussed. The summary of nanomaterials-based modulation of Aβ aggregation may help researchers to understand the critical roles in therapeutic agents and provide new insight into the exploration of more promising anti-amyloid agents and tactics in AD theranostics.

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