P2-403: CORTICAL IRON DEPOSITION IN ALZHEIMER'S DISEASE CONTRASTS WITH AGE-RELATED SUBCORTICAL DEPOSITION

Background: Alzheimer's disease (AD) is a chronic neurodegenerative disorder and the characteristics of this devastating disorder include the progressive and disabling deficits in the cognitive functions including reasoning, attention, judgment, comprehension, memory, and language. Objective: In this article, we have focused on the recent progress that has been achieved in the development of an effective AD vaccine. Summary: Currently, available treatment options of AD are limited to deliver short-term symptomatic relief only. A number of strategies targeting amyloid-beta (Aβ) have been developed in order to treat or prevent AD. In order to exert an effective immune response, an AD vaccine should contain adjuvants that can induce an effective anti-inflammatory T helper 2 (Th2) immune response. AD vaccines should also possess the immunogens which have the capacity to stimulate a protective immune response against various cytotoxic Aβ conformers. The induction of an effective vaccine’s immune response would necessitate the parallel delivery of immunogen to dendritic cells (DCs) and their priming to stimulate a Th2-polarized response. The aforesaid immune response is likely to mediate the generation of neutralizing antibodies against the neurotoxic Aβ oligomers (AβOs) and also anti-inflammatory cytokines, thus preventing the AD-related inflammation. Conclusion: Since there is an age-related decline in the immune functions, therefore vaccines are more likely to prevent AD instead of providing treatment. AD vaccines might be an effective and convenient approach to avoid the treatment-related huge expense.

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Two human metabolites rescue a C. elegans model of Alzheimer’s disease via a cytosolic unfolded protein response

Communications Biology ◽

10.1038/s42003-021-02218-7 ◽

2021 ◽

Vol 4 (1) ◽

Author(s):

Priyanka Joshi ◽

Michele Perni ◽

Ryan Limbocker ◽

Benedetta Mannini ◽

Sam Casford ◽

...

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Unfolded Protein Response ◽

Neurodegenerative Disorders ◽

C Elegans ◽

Unfolded Protein ◽

Model Of Alzheimer’S Disease ◽

Age Related ◽

Parkinson’S Diseases ◽

Protein Response

AbstractAge-related changes in cellular metabolism can affect brain homeostasis, creating conditions that are permissive to the onset and progression of neurodegenerative disorders such as Alzheimer’s and Parkinson’s diseases. Although the roles of metabolites have been extensively studied with regard to cellular signaling pathways, their effects on protein aggregation remain relatively unexplored. By computationally analysing the Human Metabolome Database, we identified two endogenous metabolites, carnosine and kynurenic acid, that inhibit the aggregation of the amyloid beta peptide (Aβ) and rescue a C. elegans model of Alzheimer’s disease. We found that these metabolites act by triggering a cytosolic unfolded protein response through the transcription factor HSF-1 and downstream chaperones HSP40/J-proteins DNJ-12 and DNJ-19. These results help rationalise previous observations regarding the possible anti-ageing benefits of these metabolites by providing a mechanism for their action. Taken together, our findings provide a link between metabolite homeostasis and protein homeostasis, which could inspire preventative interventions against neurodegenerative disorders.

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A novel orally active HDAC6 inhibitor T-518 shows a therapeutic potential for Alzheimer’s disease and tauopathy in mice

Scientific Reports ◽

10.1038/s41598-021-94923-w ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Tomohiro Onishi ◽

Ryouta Maeda ◽

Michiko Terada ◽

Sho Sato ◽

Takahiro Fujii ◽

...

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Therapeutic Potential ◽

Drug Candidate ◽

Histone Deacetylase 6 ◽

Cellular Assays ◽

Age Related ◽

Acetylation State ◽

Hdac6 Inhibitor ◽

Orally Active

AbstractAccumulation of tau protein is a key pathology of age-related neurodegenerative diseases such as Alzheimer's disease and progressive supranuclear palsy. Those diseases are collectively termed tauopathies. Tau pathology is associated with axonal degeneration because tau binds to microtubules (MTs), a component of axon and regulates their stability. The acetylation state of MTs contributes to stability and histone deacetylase 6 (HDAC6) is a major regulator of MT acetylation status, suggesting that pharmacological HDAC6 inhibition could improve axonal function and may slow the progression of tauopathy. Here we characterize N-[(1R,2R)-2-{3-[5-(difluoromethyl)-1,3,4-oxadiazol-2-yl]-5-oxo-5H,6H,7H-pyrrolo[3,4-b]pyridin-6-yl}cyclohexyl]-2,2,3,3,3-pentafluoropropanamide (T-518), a novel, potent, highly selective HDAC6 inhibitor with clinically favorable pharmacodynamics. T-518 shows potent inhibitory activity against HDAC6 and superior selectivity over other HDACs compared with the known HDAC6 inhibitors in the enzyme and cellular assays. T-518 showed brain penetration in an oral dose and blocked HDAC6-dependent tubulin deacetylation at Lys40 in mouse hippocampus. A 2-week treatment restored impaired axonal transport and novel object recognition in the P301S tau Tg mouse, tauopathy model, while a 3-month treatment also decreased RIPA-insoluble tau accumulation. Pharmaceutical inhibition of HDAC6 is a potential therapeutic strategy for tauopathy, and T-518 is a particularly promising drug candidate.

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Probable Causes of Alzheimer’s Disease

Sci ◽

10.3390/sci3010016 ◽

2021 ◽

Vol 3 (1) ◽

pp. 16

Author(s):

James David Adams

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Lactic Acid ◽

Blood Brain Barrier ◽

Transient Receptor Potential ◽

Brain Barrier ◽

Folate Intake ◽

Blood Brain ◽

Age Related ◽

The Brain

A three-part mechanism is proposed for the induction of Alzheimer’s disease: (1) decreased blood lactic acid; (2) increased blood ceramide and adipokines; (3) decreased blood folic acid. The age-related nature of these mechanisms comes from age-associated decreased muscle mass, increased visceral fat and changes in diet. This mechanism also explains why many people do not develop Alzheimer’s disease. Simple changes in lifestyle and diet can prevent Alzheimer’s disease. Alzheimer’s disease is caused by a cascade of events that culminates in damage to the blood–brain barrier and damage to neurons. The blood–brain barrier keeps toxic molecules out of the brain and retains essential molecules in the brain. Lactic acid is a nutrient to the brain and is produced by exercise. Damage to endothelial cells and pericytes by inadequate lactic acid leads to blood–brain barrier damage and brain damage. Inadequate folate intake and oxidative stress induced by activation of transient receptor potential cation channels and endothelial nitric oxide synthase damage the blood–brain barrier. NAD depletion due to inadequate intake of nicotinamide and alterations in the kynurenine pathway damages neurons. Changes in microRNA levels may be the terminal events that cause neuronal death leading to Alzheimer’s disease. A new mechanism of Alzheimer’s disease induction is presented involving lactic acid, ceramide, IL-1β, tumor necrosis factor α, folate, nicotinamide, kynurenine metabolites and microRNA.

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Correlative Microscopy to Localize and Characterize Iron Deposition in Alzheimer’s Disease

Journal of Alzheimer s Disease Reports ◽

10.3233/adr-200234 ◽

2020 ◽

Vol 4 (1) ◽

pp. 525-536

Author(s):

Steven J. Madsen ◽

Phillip S. DiGiacomo ◽

Yitian Zeng ◽

Maged Goubran ◽

Yuanxin Chen ◽

...

Keyword(s):

Oxidative Stress ◽

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Electron Microscope ◽

Oxidation State ◽

Transmission Electron Microscope ◽

Iron Deposition ◽

Direct Link ◽

Transmission Electron ◽

And Oxidative Stress

Background: Recent evidence suggests that the accumulation of iron, specifically ferrous Fe2+, may play a role in the development and progression of neurodegeneration in Alzheimer’s disease (AD) through the production of oxidative stress. Objective: To localize and characterize iron deposition and oxidation state in AD, we analyzed human hippocampal autopsy samples from four subjects with advanced AD that have been previously characterized with correlative MRI-histology. Methods: We perform scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and electron energy loss spectroscopy (EELS) in the higher resolution transmission electron microscope on the surface and cross-sections of specific iron-rich regions of interest. Results: Specific previously analyzed regions were visualized using SEM and confirmed to be iron-rich deposits using EDS. Subsequent analysis using focused ion beam cross-sectioning and SEM characterized the iron deposition throughout the 3-D volumes, confirming the presence of iron throughout the deposits, and in two out of four specimens demonstrating colocalization with zinc. Analysis of traditional histology slides showed the analyzed deposits overlapped both with amyloid and tau deposition. Following higher resolution analysis of a single iron deposit using scanning transmission electron microscope (STEM), we demonstrated the potential of monochromated STEM-EELS to discern the relative oxidation state of iron within a deposit. Conclusion: These findings suggest that iron is present in the AD hippocampus and can be visualized and characterized using combined MRI and EM techniques. An altered relative oxidation state may suggest a direct link between iron and oxidative stress in AD. These methods thus could potentially measure an altered relative oxidation state that could suggest a direct link between iron and oxidative stress in AD. Furthermore, we have demonstrated the ability to analyze metal deposition alongside commonly used histological markers of AD pathology, paving the way for future insights into the molecular interactions between Aβ, tau, iron, and other putative metals, such as zinc.

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Cryo-EM structures of tau filaments from Alzheimer’s disease with PET ligand APN-1607

Acta Neuropathologica ◽

10.1007/s00401-021-02294-3 ◽

2021 ◽

Vol 141 (5) ◽

pp. 697-708

Author(s):

Yang Shi ◽

Alexey G. Murzin ◽

Benjamin Falcon ◽

Alexander Epstein ◽

Jonathan Machin ◽

...

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Small Molecules ◽

Binding Sites ◽

Binding Activity ◽

Cortical Atrophy ◽

Binding Modes ◽

Major Site ◽

Age Related ◽

Positron Emission

AbstractTau and Aβ assemblies of Alzheimer’s disease (AD) can be visualized in living subjects using positron emission tomography (PET). Tau assemblies comprise paired helical and straight filaments (PHFs and SFs). APN-1607 (PM-PBB3) is a recently described PET ligand for AD and other tau proteinopathies. Since it is not known where in the tau folds PET ligands bind, we used electron cryo-microscopy (cryo-EM) to determine the binding sites of APN-1607 in the Alzheimer fold. We identified two major sites in the β-helix of PHFs and SFs and a third major site in the C-shaped cavity of SFs. In addition, we report that tau filaments from posterior cortical atrophy (PCA) and primary age-related tauopathy (PART) are identical to those from AD. In support, fluorescence labelling showed binding of APN-1607 to intraneuronal inclusions in AD, PART and PCA. Knowledge of the binding modes of APN-1607 to tau filaments may lead to the development of new ligands with increased specificity and binding activity. We show that cryo-EM can be used to identify the binding sites of small molecules in amyloid filaments.

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