ARTICLE | doi:10.20944/preprints202105.0556.v1
Subject: Life Sciences, Biochemistry Keywords: Alzheimer’s disease; amyloid-beta; amyloid plaques; bacterial DNA; protein aggregation
Online: 24 May 2021 (10:33:22 CEST)
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.
REVIEW | doi:10.20944/preprints202010.0195.v1
Subject: Life Sciences, Biochemistry Keywords: Autophagy; Amyloid precursor protein (APP); β‐amyloid (Aβ); mTOR; Alzheimer’s disease (AD).
Online: 9 October 2020 (11:07:53 CEST)
Autophagy refers to the degradation of cytoplasmic constituents by a lysosomal-mediated pathway, which plays a critical role in maintaining cellular homeostasis. Importantly, dysregulation of autophagy has been implicated in multiple neurodegenerative disorders. Previous studies reported that autophagy affects the processing of amyloid precursor protein (APP), thus stimulating β‐amyloid (Aβ) production in Alzheimer’s disease (AD) eventually. Although the mechanism of autophagy modulation on APP processing and its pathogenesis has not yet been fully elucidated at the molecular level, but modulation of autophagy has received considerable attention as a promising approach for the treatment of AD. In the early stage of AD, Aβ may prompt autophagy to facilitate its removal via mTOR‐independent as well as-dependent pathways. However, a recent study proposed that autophagy processes are not properly regulated as AD continues to progress, and consequently, the production of Aβ tends to accumulate rapidly. Meanwhile, a number of autophagy-related genes (Atg) as well as APP genes are also thought to influence the development of AD, which may serve as a bi‐directional link to autophagy and AD pathology. In this review, we summarized current observations related to autophagy regulation and APP processing, focusing on their dynamic modifications associated with the progression of AD. Recent findings together highlight the essential role of autophagy in the removal and clearance of APP and Aβ deposition in the pathological condition of AD.
ARTICLE | doi:10.20944/preprints202002.0018.v1
Online: 3 February 2020 (05:45:33 CET)
The amyloid fibril formation by $\alpha$-synuclein is a hallmark of various neurodegenerative disorders, most notably Parkinson's disease. Epigallocatechin gallate (EGCG) has been reported to be an efficient aggregation inhibitor of numerous proteins, among them $\alpha$-synuclein. Here we show that this applies only to a small region of relevant parameter space and that under some conditions, EGCG can even accelerate α-synuclein amyloid fibril formation through facilitating its heterogeneous primary nucleation. Furthermore, we show through quantitative seeding experiments that contrary to previous reports, EGCG is not able to re-model α-synuclein amyloid fibrils into seeding-incompetent structures. Taken together, our results paint a complex picture of EGCG as a compound that can under some conditions inhibit the amyloid fibril formation of α-synuclein, but the inhibitory action is not robust against various relevant changes in experimental conditions. Our results are important for the development of strategies to identify and characterise promising amyloid inhibitors.
ARTICLE | doi:10.20944/preprints202103.0426.v1
Subject: Life Sciences, Biochemistry Keywords: amyloid β-peptide; oligomerization; aggregation; FRET
Online: 16 March 2021 (13:29:35 CET)
Amyloid β-peptide (Aβ) oligomerization is believed to contribute to the neuronal dysfunction in Alzheimer disease (AD). Despite decades of research, many details of Aβ oligomerization in neurons still need to be revealed. Förster Resonance Energy Transfer (FRET) is a simple but effective way to study molecular interactions. Here we use a confocal microscope with a sensitive Airyscan detector for FRET detection. By live cell FRET imaging, we detect Aβ42 oligomerization in primary neurons. The neurons were incubated with fluorescently labelled Aβ42 in the cell culture medium for 24 hours. Aβ42 were internalized and oligomerized into the lysosomes/late endosomes in a concentration-dependent manner. Both the cellular uptake and intracellular oligomerization of Aβ42 were significantly higher than for Aβ40. These findings provide a better understanding of Aβ42 oligomerization in neurons.
REVIEW | doi:10.20944/preprints201808.0155.v1
Subject: Medicine & Pharmacology, Pathology & Pathobiology Keywords: amyloid diseases; biocomputing; drug design; natural antiamyloids
Online: 8 August 2018 (04:27:10 CEST)
Amyloids result from the aggregation of several unrelated proteins, due to either specific mutations or promoting intra- or extra-cellular conditions. Structurally, they are rich in intermolecular β-sheets and are the causative agents of several diseases, both neurodegenerative and systemic. It is believed that the most toxic species are small aggregates, referred to as oligomers, rather than the final fibrillar assemblies. Their mechanisms of toxicity are mostly mediated by aberrant interactions with the cell membranes, with resulting derangement of membrane-related functions. Much effort is being put in the search for natural antiamyloid agents, and/or in the development of synthetic molecules. Actually, it is well documented that the prevention of amyloid aggregation results in several cytoprotective effects. Here, we portray the state of the art in the field. Several natural compounds are effective antiamyloid agents, notably tetracyclines and polyphenols. They are generally non-specific, as documented by their partially overlapping mechanisms, and the capability to interfere with the aggregation of several unrelated proteins. Among rationally designed molecules, we mention the prominent examples of β-breakers peptides, whole antibodies and fragments thereof, and the special case of drugs contrasting transthyretin aggregation. In this framework, we stress the pivotal role of the computational approaches. When combined with biophysical methods, in several cases they have helped clarify in detail the protein/drug modes of interaction, which make it plausible that more effective drugs will be developed in the future.
ARTICLE | doi:10.20944/preprints202008.0716.v1
Subject: Medicine & Pharmacology, Behavioral Neuroscience Keywords: amyloid beta; neuropsychological assessment; machine learning; Alzheimer’s disease
Online: 31 August 2020 (09:30:08 CEST)
Substantial studies have focused on early detection of Alzheimer's disease (AD). Cerebral amyloid beta (Aβ), is hallmark of AD, can be observed in vivo via positron emission tomography imaging using amyloid tracer or cerebrospinal fluid assessment, but costly expensive. The current study aims to identify and compared predictability in magnetic resonance imaging (MRI) markers and neuropsychological markers to predict cerebral Aβ status in AD cohort using machine learning (ML) approaches. The predictability in candidate markers for cerebral Aβ status was examined by analyzing 724 participants from the ADNI-2 cohort. Demographic variables, structural MRI markers, and neuropsychological test scores were used as input in several ML algorithms to predict cerebral Aβ positivity. Out of five combination of candidate markers, neuropsychological markers with demographics showed the most cost-efficient result. A feature selection model could distinguish abnormal levels of Aβ with the predictability of 0.85, indicating the same performance with MRI-based models. The result has first to identified the predictability in MRI markers using ML approaches, and secondary to demonstrate the neuropsychological model with demographics could predict Aβ positivity, suggesting a more cost-efficient method for detecting cerebral Aβ status compared to MRI markers.
ARTICLE | doi:10.20944/preprints202010.0274.v1
Subject: Life Sciences, Biochemistry Keywords: protein aggregation; inhibition of amyloid fibril formation; antioxidants; polyphenols; cystatin C; NAC and vitamin C; amyloid fibrils; stefin B aggregation; TEM
Online: 13 October 2020 (10:49:14 CEST)
We compare the effect on amyloid fibril formation by two homologous proteins from the family of cystatins, human stefin B (stB) and cystatin C (cysC) in presence of 3 polyphenols: curcumin, resveratrol and quercetin and 2 non-phenolic anti-oxidants: vitamin C (VitC) and N-acetyl cystein (NAC). Some of the experimental data have already been presented, here we compare, further discuss and highlight the results. The amyloid fibril formation was followed by ThT fluorescence and transmission electron microscopy. Inhibitory effects on amyloid fibrillation reaction depended on anti-oxidant class and concentration. The fact that different effect of polyphenols was observed with the two cystatins; Cur acted inhibitory on stB but not on cysC fibril formation, could be explained if the 3 polyphenols would not bind to the same binding site in the fibrils core. Other differences are pointed out and discussed. Synergistic effects of VitC and chosen polyphenols on amyloid fibrilllation of human stB have been explored and are reported here for the first time.
ARTICLE | doi:10.20944/preprints201804.0079.v1
Subject: Life Sciences, Molecular Biology Keywords: Alzheimer’s disease (AD); amyloid precursor protein (APP); familial AD (FAD); sporadic AD (SAD); BACE1 inhibitors; APP-independent generation of beta amyloid
Online: 6 April 2018 (15:16:08 CEST)
The present article analyzes the results of recent clinical trials of beta secretase inhibition in sporadic Alzheimer’ disease (SAD), considers the striking dichotomy between successes in tests of BACE1 inhibitors in healthy subjects and familial AD (FAD) models versus persistent failures of clinical trials and interprets it as a confirmation of key predictions for a mechanism of APP-independent, beta secretase inhibition-resistant production of beta amyloid in SAD, previously proposed by us. In the light of this concept, FAD and SAD should be regarded as distinctly different diseases as far as beta-amyloid generation mechanisms are concerned, and whereas beta secretase inhibition would be neither applicable nor effective in treatment of SAD, the BACE1 inhibitor(s) deemed failed in SAD trials could be perfectly suitable for treatment of FAD. Moreover, targeting the aspects of AD other than cleavages of the APP by beta and alpha secretases should have analogous impacts in both FAD and SAD.
REVIEW | doi:10.20944/preprints202110.0231.v1
Subject: Life Sciences, Other Keywords: Alzheimer’s disease; magnetic resonance imaging; animal model; amyloid-beta
Online: 15 October 2021 (15:06:55 CEST)
Amyloid-beta plays an important role in the pathogenesis of Alzheimer’s disease. Aberrant amyloid-beta and tau accumulation induce neuroinflammation, cerebrovascular alterations, synaptic deficits, functional deficits, and neurodegeneration, leading to cognitive impairment. Animal models recapitulating the amyloid-beta pathology such as transgenic, knock-in mouse and rat models have facilitated the understanding of disease mechanisms and development of therapeutics targeting at amyloid-beta. There is a rapid advance in high-field MR in small animals. Versatile high-field magnetic resonance imaging (MRI) sequences such as diffusion tensor imaging, arterial spin labelling, resting-state functional MRI, anatomical MRI, MR spectroscopy as well as contrast agents have been developed for the applications in animal models. These tools have enabled high-resolution in vivo structural, functional, and molecular readouts with a whole brain field-of-view. MRI have been utilized to visualize non-invasively the amyloid-beta deposits, synaptic deficits, regional brain atrophy, impairment in white matter integrity, functional connectivity, cerebrovascular and glymphatic system in animal models of amyloidosis. Many of the readouts are translational in clinical MRI in the brain of patients with Alzheimer’s disease. In this review, we summarize the recent advance of using MRI for visualizing the pathophysiology in amyloidosis animal model. We discuss the outstanding challenges in brain imaging using MRI in small animal and propose future outlook in visualizing amyloid-beta-related alterations in brain of animal models.
REVIEW | doi:10.20944/preprints202011.0380.v1
Subject: Medicine & Pharmacology, Allergology Keywords: Bacteria; Lipopolysaccharides; Gingipains; Amyloid and Parkinson’s disease; α-Synuclein
Online: 13 November 2020 (13:22:10 CET)
Neuronal lesions in Parkinson’s disease (PD) are commonly associated with α-synuclein (α-Syn)-induced cell damage that are present both in the central and peripheral nervous systems of patients, with the enteric nervous system also being especially vulnerable. Here we bring together evidence that the development and presence of PD depends on specific sets of interlinking factors that include neuro-inflammation, systemic inflammation, α-Syn-induced cell damage, vascular dysfunction, iron dysregulation, gut and periodontal dysbiosis. We argue that there is significant evidence that bacterial inflammagens fuel this systemic inflammation, and might be central to the development of PD. We also discuss the processes whereby lipopolysaccharides may be involved in causing nucleation of proteins, including of α-Syn. Lastly, we review evidence that pre-and probiotics, as well as antibiotics and faecal transplant treatment might be valuable treatments in PD. A most important consideration, however, is that these therapeutic options need to be validated and tested in randomized controlled clinical trials. However, targeting underlying mechanisms of PD, including gut dysbiosis and iron toxicity, have potentially opened up possibilities of a wide variety of novel treatments which may relieve the characteristic non-motor deficits of PD, and may even slow the progression and/or accompanying gut-related conditions of the disease.
Subject: Medicine & Pharmacology, Nutrition Keywords: Alzheimer’s disease; lactoferrin; cognitive function; gut microbiota; amyloid β
Online: 17 February 2020 (01:00:26 CET)
Existing evidence suggest that lactoferrin might be beneficial for Alzheimer’s disease. We aimed to determine the effects of lactoferrin intervention on cognitive function from APP/PS1 mice, and possible mechanisms involved in. Both young and middle-aged male APP/PS1 mice were divided into control and lactoferrin group with 16 weeks’ intervention. Lactoferrin intervention had no effects on cognitive function from both young and middle-aged mice, and no key markers involved in Aβ, tau pathology, neuro-inflammation and synaptic plasticity were altered post lactoferrin intervention. In regards to gut microbiota profiles, in the young mice, lactoferrin elevated α diversity index including ACE and Chao 1, and reduced the relative abundance of the genera Bacteroides and Alistipes and elevated Oscillibacter, in addition, Oscillibacter, Anaerotruncus, EF096579_g, EU454405_g, Mollicutes_RF39, EU474361_g, EU774448_g, and EF096976_g were specifically abundant post Lf intervention via LEfSe analysis. In the middle-aged mice, the relative abundance of the phylum Proteobacteria, as well as the genera Oscillospira, Coprococcus and Ruminococcus was significantly reduced post Lf intervention, additionally, S24_7, Bacteroidia, Bacteroidetes and Methylobacterium were specific via LEfSe analysis post lactoferrin intervention. In conclusion, dietary lactoferrin might be beneficial for gut microbiota homeostasis although might have no effects on cognition.
ARTICLE | doi:10.20944/preprints201909.0273.v2
Subject: Life Sciences, Biophysics Keywords: amyloid; virus; nucleation; loss-of-function; Alzheimer's; Parkinson's; prion; protein-only
Online: 19 November 2019 (03:53:09 CET)
Amyloids are fibrillar protein aggregates that are associated with diseases such as Alzheimer’s disease, Parkinson’s disease, type II diabetes and Creutzfeldt–Jakob disease. The process of amyloid aggregation involves three pathological protein transformations; from natively-folded conformation to the cross-β conformation, from biophysically soluble to insoluble, and from biologically functional to non-functional. While amyloids share a similar cross-β conformation, the biophysical transformation can either take place spontaneously via a homogeneous nucleation mechanism (HON) or catalytically on an exogenous surface via a heterogeneous nucleation mechanism (HEN). Here, we postulate that the different nucleation pathways can serve as a mechanistic basis for an etiological classification of amyloidopathies, where hereditary forms generally follow the HON pathway, while sporadic forms follow surface-induced (including microbially-induced) HEN pathways. Furthermore, the conformational and biophysical amyloid transformation results in loss-of-function (LOF) of the original natively-folded and soluble protein. This LOF can, at least initially, be the mechanism of amyloid toxicity even before amyloid accumulation reaches toxic levels. By highlighting the important role of non-protein species in amyloid formation and LOF mechanisms of toxicity, we propose a generalized mechanistic framework that could help better understand the diverse etiology of amyloid diseases and offer new opportunities for therapeutic interventions including replacement therapies.
ARTICLE | doi:10.20944/preprints201810.0766.v1
Subject: Medicine & Pharmacology, Pharmacology & Toxicology Keywords: Nuclear transcription, endothelium, atherosclerosis, serum amyloid A, vascular function
Online: 2 November 2018 (14:04:15 CET)
The acute phase protein serum amyloid A (SAA) is associated with endothelial dysfunction and early-stage atherogenesis. Stimulation of vascular cells with SAA increases gene expression of pro-inflammation cytokines and tissue factor (TF). Activation of the transcription factor, nuclear factor kappa-B (NFkB), may be central to SAA-mediated endothelial cell inflammation, dysfunction and pro-thrombotic responses, while targeting NFkB with a pharmacologic inhibitor, BAY11-7082, may mitigate SAA activity. Human carotid artery endothelial cells (HCtAEC) were pre-incubated (1.5 h) with 10 µM BAY11-7082 or vehicle (control) followed by SAA (10 μg/mL; 4.5 h). Under these conditions gene expression for TF and TNF increased in SAA-treated HCtAEC and pre-treatment with BAY11-7082 significantly (TNF) and marginally (TF) reduced mRNA expression. Intracellular TNF and IL-6 protein also increased in HCtAEC supplemented with SAA and this expression was inhibited by BAY11-7082. Supplemented BAY11-7082 also significantly decreased SAA-mediated leukocyte adhesion to apolipoprotein E-deficient mouse aorta in ex vivo vascular flow studies. In vascular function studies, isolated aortic rings pre-treated with BAY11-7082 prior to incubation with SAA showed improved endothelium-dependent vasorelaxation and increased vascular cGMP content. Together these data suggest that inhibition of NFkB activation may protect endothelial function by inhibiting the pro-inflammatory and pro-thrombotic activities of SAA.
REVIEW | doi:10.20944/preprints202109.0073.v1
Subject: Life Sciences, Molecular Biology Keywords: Mitochondrial dysfunction; Alzheimer's disease; Parkinson's disease; Neurodegeneration; Amyloid beta; Parkin
Online: 3 September 2021 (16:01:26 CEST)
Mitochondrial dysfunctions remained a pivotal mechanism in manifold neurodegenerative diseases. Mitochondrial homeostasis within the cell is an essential aspect of cell biology. Mitochondria which is also known as the power-generating set of the cell, have a dominant role in several processes associated with the genomic integrity and cellular equilibrium maintenance. They are involved in maintaining optimal cells functioning and guidance from possible DNA damage which could lead to mutations and onset of diseases. Conversely, system perturbations which could be due to environmental factors or senescence induce changes in the physiological balance and result in the mitochondrial functions impairment. The focal point of this review focuses on mitochondrial dysfunction as a significant condition in the onset of neuronal disintegration. We explain the pathways associated with the dysfunction of the mitochondria which are common amongst the most recurring neurodegenerative diseases including Alzheimers and Parkinsons disease. Do mitochondrial dysfunctions represent an early event in causing a shift towards neuropathological processes?
Subject: Life Sciences, Biochemistry Keywords: copper; amyloid-β peptides; Alzheimer’s disease; oxidative stress; dopamine; neurodegeneration.
Online: 26 April 2021 (13:23:52 CEST)
The redox chemistry of copper(II) is strongly modulated by the coordination to amyloid-β peptides and by the stability of the resulting complexes. Amino terminal copper and nickel binding motifs (ATCUN) identified in truncated Aβ sequences starting with Phe4 show very high affinity for copper(II) ions. Herein, we study the oxidase activity of [Cu-Aβ4-x] and [Cu-Aβ1-x] complexes toward dopamine and other catechols. The results show that the CuII-ATCUN site is not redox-inert, the reduction of the metal is induced by coordination of catechol to the metal and occurs through an inner sphere reaction. The generation of a ternary [CuII-Aβ-catechol] species determines the efficiency of the oxidation, although the reaction rate is ruled by re-oxidation of the CuI complex. In addition to the N-terminal coordination site, the two vicinal histidines, His13 and His14, provide a second Cu-binding motif. Catechol oxidation studies together with structural insight from the mixed dinuclear complexes Ni/Cu-Aβ4-x reveal that the His-tandem is able to bind CuII ions independently of the ATCUN site, but the N-terminal metal complexation reduces the conformational mobility of the peptide chain, preventing the binding and oxidative reactivity toward catechol of CuII bound to the secondary site.
ARTICLE | doi:10.20944/preprints201705.0126.v1
Subject: Biology, Other Keywords: amyloid peptides; androgen receptor; nuclear receptor; aggregation; atomic force microscopy
Online: 16 May 2017 (17:48:54 CEST)
The human androgen receptor (AR) is a ligand inducible transcription factor harboring an amino terminal domain (AR-NTD) hosting the ligand independent activation function. AR-NTD is intrinsically disordered and display aggregation properties conferred by the presence of a poly-glutamine (polyQ) sequence of 22 residues. The length of the polyQ sequence, as well as the presence of adjacent sequence motifs modulate this aggregation property. AR-NTD contains also a conserved sequence motif KELCKAVSVSM that displays an intrinsic property to form amyloid fibrils under mild oxidative conditions of its conserved cysteine residue. As peptide sequences with intrinsic ability to oligomerize are reported to have an impact on the aggregation of polyQ tract, we determined the effect of the KELCKAVSVSM on the polyQ stretch in the context of the AR NTD, using Atomic Force Microscopy (AFM). Here, we present evidence for a crosstalk between the amyloidogenic properties of the KELCKAVSVSM motif and the polyQ stretch at the AR NTD.
HYPOTHESIS | doi:10.20944/preprints202012.0813.v1
Subject: Medicine & Pharmacology, Allergology Keywords: Alzheimer’s disease; beta-amyloid; protease; membrane; membrane channel; lysosome; autophagy; mitochondrion
Online: 31 December 2020 (13:32:26 CET)
Alzheimer's disease (AD) is the most common cause of dementia and affects millions of people around the world. Neuronal death in AD is initiated by the toxic action of oligomeric amyloid-β (Aβ) peptides. The formation of membrane channels by Aβ is a primary molecular action and does not require any other proteins. Channels are formed by short amyloid fragments faster and more frequently than by full-length peptides. The channel formation is dependent on an electrostatic interaction between a positively charged peptide and a negatively charged membrane. Negative membranes can be found in several locations of a cell – the inner leaflet of plasma membrane, mitochondria, and lysosomes, which all are well-known cellular targets in AD. Considering that the amyloid enters a cell by endocytosis and is exposed to lysosomal enzymes, we propose the amyloid degradation toxicity hypothesis. Endopeptidases degrade the endocytosed peptide. Produced fragments form membrane channels, which can transfer various ions (including protons) and even relatively large compounds. The neutralization of lysosomal content inactivates enzymes, which fails the whole system of recycling cellular content, including autophagy. The permeabilization of lysosomes could also lead to cell death through necrotic and apoptotic mechanisms. We discuss several mechanisms that describe how amyloid degradation products reach plasma and mitochondrial membranes, and form membrane channels. The pathogenesis of AD is discussed at various levels in a context of how the primary molecular mechanism of membrane channel formation could progress into the disease state. The discussion starts at the molecular level and extends to why the development of a disease takes years and is closely associated with aging. The proposed hypothesis offers an interpretation to several clinical observations such as the involvement of iron metabolism and an inverse association between developing Alzheimer's disease and cancer. Predictions about potential biomarkers and effectiveness of future treatments are discussed.
ARTICLE | doi:10.20944/preprints202011.0001.v1
Subject: Medicine & Pharmacology, Allergology Keywords: Alzheimer’s Disease; Task Performance; Cognition; Human Activities; Amyloid Beta Protein; Dementia
Online: 2 November 2020 (08:06:39 CET)
The purpose of this study is to explore the effects of dual-task training, including cognitive tasks, on cognitive and bodily functioning and β-amyloid levels in Alzheimer's dementia patients. The subjects were 34 inpatients diagnosed with Alzheimer's dementia at a nursing hospital located in Gyeongsansi, South Korea. The patients were randomly divided into a dual-task group (n = 16) and a single-task group (n = 18). The dual-task group performed cognitive tasks at the same time as exercising tasks, while the single-task group performed only exercise tasks. Each group was trained for 30 minutes three times a week for eight weeks. The Mini-Mental State Examination was used to measure the patients’ cognitive function. Static and dynamic balance were measured to evaluate bodily functioning. Static balance was measured using Biorescue, while dynamic balance was measured using the Berg Balance Scale. Blood analysis was performed to measure levels of β-amyloid, which is known to cause Alzheimer's dementia. Both groups exhibited statistically significant improvements in gait function after the training (p < .05). The dual-task group exhibited statistically significant differences in cognitive function, static and dynamic balance function, and β-amyloid levels after training (p < .05). A significant difference was observed between the two groups (p < .05). Dual-task activities were found to be effective in improving cognitive and bodily functioning and reducing β-amyloid levels in Alzheimer's dementia patients. Therefore, dual-task training is thought to be an effective method of treating and preventing Alzheimer's dementia.
ARTICLE | doi:10.20944/preprints202205.0184.v1
Subject: Life Sciences, Molecular Biology Keywords: amyloid precursor protein; photothrombotic stroke; ischemia; alpha-secretase; beta-secretase; gamma-secretase
Online: 13 May 2022 (08:39:09 CEST)
Photothrombotic stroke (PTS) stimulates the level of N- and C-terminal fragments of Amyloid precursor protein (APP) growth in the cytoplasm of ischemic penumbra cells not earlier but at 24 hours. Here we have shown that APP fragments are visualized in thin unmyelinated fibers of neurons, in containing mitochondria large fibers and in synapses but absent in the nuclei. At 24 hours after PTS, some elements of the destroyed tissue accumulated a significant amount of APP protein. The level of ADAM10 α-secretase decreased on the first day after PTS in the rat brain cortex and ADAM-10 co-localized with the lipid raft marker caveolin-1. PTS caused no changes in the level of β-secretase BACE1 either on the first day after PTS or in the early recovery period. The expression of proteins of the γ-secretase complex: presenilin-1 and nicastrin increased in astrocytes, but not in penumbra neurons after PTS. The β-secretase inhibitor LY2886721 did not affect the infarct size of the mouse cerebral cortex and the level of apoptosis of cells in the perifocal region after PTS. Whereas the inhibitor of γ-secretase DAPT reduced the expression of glial fibrillary acidic protein (GFAP) in astrocytes, prevented the growth of apoptosis of mouse cerebral cortex cells reducing the infarct volume on the 7th and 14th days after PTS. DAPT may be considered as a drug for stroke therapy.
ARTICLE | doi:10.20944/preprints202204.0030.v1
Subject: Life Sciences, Virology Keywords: Zika virus; unfolded protein response; ER stress; oligomer; disulfide bond amyloid aggregates
Online: 6 April 2022 (05:24:41 CEST)
Flaviviruses replicate in membrane factories associated with the endoplasmic reticulum (ER). Significant levels of flavivirus viral protein accumulation contribute to ER stress. As a consequence, the host cell exhibits an Unfolded Protein Response (UPR), subsequently stimulating appropriate cellular responses such as adaptation, autophagy or apoptosis. The correct redox conditions of this compartment are essential to form native disulfide bonds in proteins. ZIKA virus (ZIKV) has ability to induce persistent ER stress leading to activation of UPR pathways. In this study, we wondered whether ZIKV affects the redox balance and consequently the oxidative protein folding in the ER. We found that ZIKV replication influences redox state leading to aggregation of viral envelope protein as amyloid-like structures in the infected cells.
ARTICLE | doi:10.20944/preprints202202.0012.v1
Subject: Medicine & Pharmacology, Nutrition Keywords: Human Insulin, Amyloid Fibrils; Protein aggregation; Amorphous aggregates; Aromatic Compounds; Polyphenol; Pyrogallol
Online: 1 February 2022 (12:46:35 CET)
One of the major problems caused by repeated subcutaneous insulin injections in diabetic patients is insulin amyloidosis. Understanding the molecular mechanism of amyloid fibril formation of insulin and finding effective compounds to its inhibit or eliminate is very important and extensive research has been done on it. In this study, the anti-amyloidogenic and destabilizing effects of the pyrogallol, as a phenolic compound, on human insulin protein were investigated by CR absorbance, ThT and ANS fluorescence, FTIR spectroscopy and atomic force microscopy. According to the obtained results, the formation of amyloid fibrils at pH 2.0 and 50 °C was confirmed by CR, ThT, ANS, FTIR assays. Microscopic images also showed the twisted and long structures of amyloid fibrils. Simultaneous incubation of the protein with pyrogallol at different concentrations reduced the intensities of CR, ThT and ANS in a dose-dependent manner and no trace of fibrillar structures was observed in the microscopic images. FTIR spectroscopy also showed that the position of amide I band in the spectrum of samples containing pyrogallol was shifted. Based on the findings in this study, it can be concluded that pyrogallol can be effective in preventing and suppressing human insulin amyloid fibrils.
ARTICLE | doi:10.20944/preprints202004.0318.v1
Subject: Life Sciences, Other Keywords: Alzheimer’s disease; amyloid β; β-secretase; bax; caspase; lamiaceae; mint; oxidative stress
Online: 19 April 2020 (03:57:56 CEST)
Alzheimer’s disease (AD) is a progressive neurodegenerative disorder that develops as a consequence of different factors such as oxidative stress and accumulation of the protein amyloid β (Aβ) in the brain, resulting in apoptosis of neuronal cells. The search for a treatment for this disorder is essential as current medications are limited to alleviating symptoms and palliative effects. The aim of this study is to investigate the effects of mint extracts on selected mechanisms implicated in the development of AD. To enable a thorough investigation of mechanisms, including effects on -secretase (the enzyme the leads to the formation of A), on Aβ aggregation, and on oxidative stress and apoptosis pathways, a neuronal cell model, SH-SY5Y cells was selected. Six Mentha taxa were investigated for their in vitro β-secretase (BACE) and Aβ-aggregation inhibition activities. Also, their neuroprotective effects on H2O2-induced oxidative stress and apoptosis in SH-SY5Y cells were evaluated through caspase activity. Real-time PCR and Western blot analysis were carried out for the two most promising extracts to determine their effects on signalling pathways in SH-SY5Y cells. All mint extracts had strong BACE inhibition activity. M. requienii extracts showed excellent inhibition of Aβ-aggregation, while other extracts showed moderate inhibition. M. diemenica and M. requienii extracts lowered caspase activity. Exposure of SH-SY5Y cells to M. diemenica extracts resulted in a decrease in the expression of pro-apoptotic protein, Bax, and an elevation in the anti-apoptotic protein, Bcl-xL, potentially mediated by down-regulation of ASK1-JNK pathway. These results indicate that mint extracts could prevent the formation of Aβ and also could prevent their aggregation if they had already formed. M. diemenica and M. requienii extracts have potential to suppress apoptosis at the cellular level. Hence, mint extracts could provide a source of efficacious compounds for a therapeutic approach for AD.
REVIEW | doi:10.20944/preprints201809.0075.v1
Subject: Biology, Other Keywords: A; aggregation; amyloid; APP; misfolding; prion protein; prion-like; PrP; seeds; tau
Online: 4 September 2018 (16:51:56 CEST)
The misfolding and aggregation of proteins is the neuropathological hallmark of numerous diseases including Alzheimer’s disease, Parkinson’s disease, and prion diseases. It is believed that misfolded and abnormal -sheets forms of wild-type proteins are the vectors of these diseases by acting as seeds for the aggregation of endogenous proteins. Cellular prion protein (PrPC) is a glycosyl-phosphatidyl-inositol (GPI) anchored glycoprotein which is able to misfold to a pathogenic isoform PrPSc, the causative agent of prion diseases which present as sporadic, dominantly inherited and transmissible infectious disorders. Increasing evidence highlight the importance of prion-like seeding as a mechanism for pathological spread in Alzheimer’s disease and tauophaty, as well as other neurodegenerative disorders. Here, we report the latest findings on the mechanisms controlling protein folding, focusing on the ER quality control of GPI-anchored proteins and describe the “prion-like” properties of amyloid- and tau assemblies. Furthermore, we highlight the importance of pathogenic assemblies interactions with protein and lipid membrane components and their implications in both prion and Alzheimer’s diseases.
ARTICLE | doi:10.20944/preprints201806.0463.v1
Subject: Life Sciences, Molecular Biology Keywords: α-synuclein; amyloid fibrils; fibrillogenesis; thioflavin T; equilibrium microdialysis; binding parameters; structural polymorphism
Online: 28 June 2018 (10:50:40 CEST)
In this work α-synuclein amyloid fibrils, formation of which is a biomarker of the Parkinson’s disease, were investigated with the use of fluorescent probe thioflavin T (ThT). Experimental conditions of the protein fibrillogenesis were chosen so that a sufficient number of continuous measurements can be performed to characterize and analyze all stages of this process. The reproducibility of fibrillogenesis and the structure of the obtained aggregates (that is a critical point for their further investigation) were proved using a wide range of physical-chemical methods. For determination of ThT—α-synuclein amyloid fibrils binding parameters sample and reference solutions were prepared with the use of equilibrium microdialysis. By absorption spectroscopy of these solutions ThT—fibrils binding mode with the binding constant about 104 M−1 and stoichiometry of ThT per protein molecule about 1:8 was observed. Fluorescence spectroscopy of the same solutions with the subsequent correction of the recorded fluorescence intensity on the primary inner filter effect allowed to determine another mode of ThT binding to fibrils with the binding constant about 106 M−1 and stoichiometry about 1:2500. Analysis of photophysical characteristics of the dye molecules bound to the sites of different binding modes allowed to assume the possible localization of these sites. Obtained differences in the ThT binding parameters to amyloid fibrils formed from α-synuclein and other amyloidogenic proteins, as well as in the photophysical characteristics of the bound dye, confirmed the hypothesis of amyloid fibrils polymorphism.
ARTICLE | doi:10.20944/preprints201805.0380.v1
Subject: Chemistry, General & Theoretical Chemistry Keywords: molecular dynamics simulation; biophenols; natural compounds; amyloid fibrils; Alzheimer’s disease; ligand-protofiber interactions
Online: 27 May 2018 (13:09:22 CEST)
One of the principal hallmarks of Alzheimer’s disease (AD) is related to the aggregation of amyloid-β fibrils in an insoluble form in the brain, also known as amyloidosis. Therefore, a prominent therapeutic strategy against AD consists either in blocking the amyloid aggregation and/or destroying the already formed aggregates. Natural products have shown significant therapeutic potential as amyloid inhibitors from in vitro studies as well as in vivo animal tests. In this study, the interaction of five natural biophenols (curcumin, dopamine, (-)-Epigallocatechin-3-gallate, Quercetin, and Rosmarinic acid) with the amyloid-β(1-40) fibrils has been studied through computational simulations. The results allowed the identification and characterization of the different binding modalities of each compounds and their consequences on fibril dynamics and aggregation. It emerges that the lateral aggregation of the fibrils is strongly influenced by the intercalation of the ligands, which modulate the double-layered structure stability.
ARTICLE | doi:10.20944/preprints201706.0060.v1
Subject: Materials Science, Biomaterials Keywords: β-amyloid 42; differential pulse voltammetry; Neuro-degenerative disorders; ferrocyanide/ferricyanide redox couple
Online: 13 June 2017 (18:14:57 CEST)
A simple in vitro biosensor for the detection of β-amyloid 42 in phosphate-buffer saline (PBS) and undiluted human serum was fabricated and tested based on our platform sensor technology. The bio-recognition mechanism of this biosensor was based on the effect of the interaction between antibody and antigen of β-amyloid 42 to the redox couple probe of K4Fe (CN) 6 and K3Fe (CN) 6. Differential pulse voltammetry (DPV) served as the transduction mechanism measuring the current output derived from the redox coupling reaction. The biosensor was a three-electrode electrochemical system, and the working and counter electrodes were 50 nm thin gold film deposited by sputtering technique. The reference electrode was a thick-film printed Ag/AgCl electrode. Laser ablation technique was used to define the size and structure of the biosensor. Cost-effective roll-to-roll manufacturing process was employed in the fabrication of the biosensor making it simple and relatively inexpensive. Self-assembled monolayers (SAM) of 3-Mercaptopropionic acid (MPA) was employed to covalently immobilize the thiol group on the gold working electrode. A carbodiimide conjugation approach using N-(3-dimethylaminopropyl)-N’-ethylcarbodiimide hydrochloride (EDC) and N–hydroxysuccinimide (NHS) was undertaken for cross-linking antibody of β-amyloid 42 to the carboxylic groups on one end of the MPA. The antibody concentration of β-amyloid 42 used was 18.75µg/mL. The concentration range of β-amyloid 42 in this study was from 0.0675µg/mL to 0.5µg/mL for both PBS and undiluted human serum. DPV measurements showed excellent response in this antigen concentration range. Interference study of this biosensor was carried out in the presence of Tau protein antigen. Excellent specificity of this β-amyloid 42 biosensor was demonstrated without interference by other species such as T-tau protein.
ARTICLE | doi:10.20944/preprints202109.0320.v1
Subject: Biology, Physiology Keywords: music; blood-brain barrier; lymphatic system; amyloid-β protein; detrended fluctuation analysis; electroencephalographic patterns.
Online: 20 September 2021 (09:02:40 CEST)
The lymphatic system of the brain meninges and head plays a crucial role in the clearance of amyloid-β protein (Aβ), a peptide thought to be pathogenic in Alzheimer’s disease (AD), from the brain. The development of methods to modulate lymphatic clearance of Aβ from the brain coild be a revolutionary step in the therapy of AD. The opening of the blood-brain barrier (OBBB) by focused ultrasound is considered as a possible tool for stimulation of clearance of Aβ from the brain of humans and animals. Here, we propose an alternative method of non-invasive music-induced OBBB that is accompanied by the activation of clearance of fluorescent Aβ (Fαβ) from the mouse brain. Using confocal imaging, fluorescence microscopy and magnetic resonance tomography, we clearly demonstrate that OBBB by music stimulates the movement of Fαβ and Omniscan in the cerebrospinal fluid and lymphatic clearance of Fαβ from the brain. We propose the extended detrended fluctuation analysis (EDFA) as a promising method for the identification of OBBB markers in the electroencephalographic (EEG) patterns. These pilot results suggest that music-induced OBBB and the EDFA analysis of EEG can be a non-invasive, low cost, labelling free, clinical perspective and completely new approach for the treatment and monitoring of AD.
COMMUNICATION | doi:10.20944/preprints202109.0133.v1
Subject: Medicine & Pharmacology, Clinical Neurology Keywords: cerebrospinal fluid; alpha-synuclein; skin biopsy; seeded aggregation assays; tau, amyloid; Lewy body dementia
Online: 7 September 2021 (16:26:51 CEST)
The Lewy Body Dementia Association (LBDA) held a virtual event, the LBDA Biofluid/Tissue Biomarker Symposium, on January 25, 2021, to present advances in biomarkers for Lewy Body Dementia (LBD), which includes Dementia with Lewy Bodies (DLB) and Parkinson's Disease Dementia (PDD). The meeting featured eight internationally known scientists from Europe and the United States and attracted over 200 scientists and physicians from academic centers, the National Institutes of Health and the pharmaceutical industry. Methods for confirming and quantifying the presence of Lewy body and Alzheimer pathology as well as novel biomarkers were discussed.
ARTICLE | doi:10.20944/preprints202107.0564.v1
Subject: Medicine & Pharmacology, Allergology Keywords: Neurological activity; GC-MS; ADMET profile; Molecular Docking; Beta-amyloid precursor protein; Alzheimer’s disease
Online: 26 July 2021 (10:27:40 CEST)
Medicinal plants possess a surplus of novel and biologically active secondary metabolites that are responsible for counteracting diseases. Traditionally, Gomphandra tetrandra (Wall.) Sleumer is used to treat mental disorders. The present research was designed to explore phytochemicals from the ethanol leaf extract of Gomphandra tetrandra (Wall.) Sleumer to identify the potential pharmacophore(s) in the treatment of neurological disorders. The chemical compounds of the experimental plant were identified through GC-MS analysis. Besides, in-vitro antioxidant activity was assessed using different methods. Furthermore, in-vivo neurological activity was assessed in Swiss-albino mice. Computer aided analysis was appraised to determine the best-fit phytoconstituent of a total of fifteen identified compounds in the experimental plant extract against beta-amyloid precursor protein. The experimental extract revealed fifteen compounds in GC-MS analysis and the highest content was 9, 12, 15-octadecatrienoic acid (Z, Z, Z). Also, the extract showed potent anti-oxidant activity in in-vitro assays. Furthermore, in in-vivo neurological assays, the extract disclosed significant (p<0.05) neurological activity. The most favorable phytochemicals as neurological agents were selected via ADMET profiling and molecular docking was studied with beta-amyloid precursor protein. Moreover, in the computer aided study, 1, 5-Diphenyl-2H-1, 2, 4-triazoline-3-thione (Pub Chem CID: 2802516) was more active than other identified compounds with strong binding affinity to beta-amyloid precursor protein. The present in vivo and in silico studies revealed neuropharmacological features of G. tetrandra leaves extract as a natural agent against neurological disorders, especially Alzheimer’s disease.
ARTICLE | doi:10.20944/preprints202105.0032.v1
Subject: Medicine & Pharmacology, Allergology Keywords: Alzheimer’s disease; cellular prion protein; amyloid β and PrP interaction in Alzheimer’s; BACE1; Aβ
Online: 5 May 2021 (10:45:04 CEST)
Alzheimer’s disease (AD) is the most common cause of dementia worldwide. Pathological deposits of neurotoxin proteins within the brain, such as amyloid-Beta and hyperphosphorylated tau tangles, are prominent features in AD. The prion protein (PrP) is involved in neurodegeneration via its conversion from the normal cellular form PrPc, to the infection form PrP Sc. Some studies indicated that posttranslationally modified PrPc isoforms plays a fundamental role in AD pathological progression. Several studies have shown that interaction of Aβ oligomers with N-terminal residues of the PrPc protein region appears critical for neuronal toxicity. The PrPc-Aβ binding always occur in AD brains and is never detected in nondemented controls and the binding of Aβ aggregates to PrPc is restricted to the N-terminus of PrPc.
Subject: Keywords: paraoxonases; oxidative stress; Alzheimer’s disease; brain; Tg2576 mice; astrocytes; hippocampus; amyloid-β; microglia; neurons
Online: 18 December 2020 (11:53:45 CET)
Background: Brain oxidative lipid damage and inflammation are common in neurodegenerative diseases such as Alzheimer’s disease (AD). Paraoxonase-1 and 3 (PON1 and PON3) protein expression have been described in tissues with no PON1 and PON3 gene expression. In the present study, we aimed to examine differences in PON1 and PON3 protein expression in the brain of a mouse model of AD. Methods: We used peroxidase-based and fluorescence-based immunohistochemistry in 5 brain regions (olfactory bulb, forebrain, posterior midbrain, hindbrain and cerebellum) of transgenic (Tg2576) mice with the Swedish mutation (KM670/671NL) responsible for a familial form of AD and corresponding wild-type mice. Results: We found intense PON1 and PON3 positive staining in star-shaped cells surrounding Aβ plaques in all Tg2576 mouse brain regions studied. Although we could not co-localize PON1 and PON3 with astrocytes, brain star-shaped cells, we found some co-localization of PON3 with microglia. Conclusions: These results suggest that 1) PON1 and PON3 cross the blood-brain barrier in discoidal HDLs and are transferred to specific brain cell types, and 2) PON1 and PON3 play an important role in preventing oxidative stress and lipid peroxidation in particular cell types, likely astrocytes and microglia, in AD pathology, and potentially in other neurodegenerative diseases
ARTICLE | doi:10.20944/preprints201705.0144.v1
Subject: Biology, Animal Sciences & Zoology Keywords: Alzheimer’s disease (AD); amyloid-β1-42(Aβ1–42); Lycium ruthenicum Murray (LRA); neuroprotective effect
Online: 19 May 2017 (06:26:45 CEST)
Alzheimer’s disease (AD) is an age-related neurodegenerative disease and is clinically characterized by cognitive impairment, memory loss, and personality disorder. Oligomers of amyloid beta-peptides (Aβ) and enhanced oxidative stress in senile plaques are prevalent pathologic hallmarks of AD. In this study, we detected the behavioral performance of Lycium ruthenicum Murray anthocyanin (LRA) -treated rats using the Morris water maze test and then investigated the effect of LRA on oxidative damage, neuronal apoptosis, and inflammatory response induced by Aβ1–42. Our results showed that LRA treatment markedly ameliorated the behavioral performance of Aβ1–42-induced rats and reduced the level of malondialdehyde, formation of protein carbonyl, and 8-hydroxy-2’-deoxygua-nosine. Furthermore, LRA also inhibited activated astrocytes and neuroinflammation via suppression of glial fibrillary acidic protein and tumor necrosis factor-alpha in the hippocampus of Aβ1–42-treated rat brain. These data suggest that LRA could be a potential anti-oxidant and anti-neuroinflammatory agent for the treatment of AD.
HYPOTHESIS | doi:10.20944/preprints202108.0115.v1
Subject: Medicine & Pharmacology, Allergology Keywords: beta-amyloid toxicity, proteolytic digestion, membrane channel, intracellular ion disturbances, calcium homeostasis, intracellular pH, lysosome
Online: 4 August 2021 (13:19:50 CEST)
In this manuscript, we reassess the data on beta-amyloid-induced changes of intracellular ions concentrations published previously by Abramov et al. (2003, 2004). Their observations made using high-resolution confocal microscopy with fast temporal resolution of images formed by fluorescent ion-sensitive fluorescent probes in living cells represent an unequivocal support for the amyloid channel theory. However, closer look reveals multiple facts which cannot be explained by channel formation in plasma membrane. Recently proposed amyloid degradation toxicity hypothesis provides the interpretation to these facts by considering that channels are formed in the lysosomal membranes.
REVIEW | doi:10.20944/preprints202103.0365.v1
Subject: Medicine & Pharmacology, Clinical Neurology Keywords: Real-time MR imaging; CSF; cilia sensing; aquaporin; nitric oxide; amyloid-ß; glymphatic system; hydrocephalus
Online: 15 March 2021 (10:36:20 CET)
With the advent of real-time MRI, the motion and passage of cerebrospinal fluid can be visualized without gating and exclusion of low-frequency waves. This imaging modality gives insights into low-volume, rapidly oscillating cardiac-driven movement as well as sustained, high-volume, slowly oscillating inspiration-driven movement.Inspiration means a spontaneous or artificial increase in the intrathoracic dimensions independent of body position. Alterations in thoracic diameter enable the thoracic and spinal epidural venous compartments to be emptied and filled, producing an upward surge of cerebrospinal fluid inside the spine during inspiration; this surge counterbalances the downward pooling of venous blood toward the heart.Real-time MRI, as a macroscale in vivo observation method, could expand our knowledge of neurofluid dynamics, including how astrocytic fluid preloading is adjusted and how brain buoyancy and turgor are maintained in different postures and zero gravity.Along with these macroscale findings, new microscale insights into aquaporin-mediated fluid transfer, its sensing by cilia and its tuning by nitric oxide will be reviewed. By incorporating clinical knowledge spanning several disciplines, certain disorders—congenital hydrocephalus with Chiari malformation, idiopathic intracranial hypertension and adult idiopathic hydrocephalus—are interpreted and reviewed according to current concepts, from the basics of the interrelated systems to their pathology.
ARTICLE | doi:10.20944/preprints201811.0142.v1
Subject: Life Sciences, Other Keywords: melatonin, protocatechuic acid, hydroxytyrosol, α-synuclein, toxicity, amyloid aggregation, neurodegeneration, Parkinson´s disease, olive oil, wine
Online: 6 November 2018 (13:09:18 CET)
The abnormal assembly of α-synuclein (α-Syn) is an initial step in the formation of Lewy bodies in the brain, which finally causes the neuronal death, being considered as a pathological hallmark in Parkinson’s disease (PD). Certain food bioactives or their metabolites at very low concentrations can trespass the blood brain barrier (BBB) that might, thereafter, act simultaneously. The aim of this work was to evaluate the inhibitory and destabilising capacities on α-Syn kinetics and the neuroprotective effects of three well-known bioactive compounds able to cross the BBB and present in foods; melatonin (MEL), protocatechuic acid (PCA) and hydroxytyrosol (HT), and their combinations. For this purpose, different in vitro techniques (Thioflavin T (ThT), Transmission Electronic Microscopy (TEM), electrophoresis and MTT assay) were used. All tested compounds and their combinations were able to abolish the toxicity induced by α-Syn. In addition, the combination of PCA (100 µM) +HT (100 µM) showed the highest inhibitory effect against α-Syn fibril formation and destabilises α-Syn fibrils (88 and 62%, respectively). This is the first time that MEL, PCA and HT prove a joint effect against α-Syn aggregation and toxicity when they are tested together.
Subject: Life Sciences, Biochemistry Keywords: amyloid-β; endotoxin; short chain fatty acids; clasmatodendrosis; cytokines; neurovascular unit; vagus nerve; Toll-like Receptor 4
Online: 26 April 2021 (13:22:47 CEST)
Much evidence has accumulated over the past decade in favor of a significant association between dysbiosis, neuroinflammation and neurodegeneration. Presently, the pathogenetic mechanisms triggered by molecules produced by the altered microbiota, also responsible for the onset and evolution of Alzheimer Disease will be described. Our attention will be focused on the role of astrocytes and microglia. Numerous studies have progressively demonstrated how these glial cells are important to ensure an adequate environment for neuronal activity in healthy conditions. Furthermore, it is becoming evident how both cell types can mediate the onset of neuroinflammation and lead to neurodegeneration when subjected to pathological stimuli. Based on this information, the role of major microbiota products in shifting the activation profiles of astrocytes and microglia from a healthy to a diseased state will be discussed focussing on Alzheimer Disease pathogenesis.
REVIEW | doi:10.20944/preprints202110.0197.v1
Subject: Medicine & Pharmacology, Cardiology Keywords: AGING; Age-related comorbidities; Angiotensin-Converting Enzyme; Amyloid-degrading enzyme; Alzheimer’s disease; Dementia; Hypertension; Life extension; Stress resistance
Online: 13 October 2021 (11:04:43 CEST)
A recent report from the American Heart Association in 2018 shows that over 103 million American adults have hypertension. The angiotensin-converting enzyme (ACE) (EC 22.214.171.124) is a dipeptidyl carboxylase that, when inhibited, can reduce blood pressure through the renin-angiotensin system. ACE inhibitors are used as a first-line medication to be prescribed to treat hypertension, chronic kidney disease, heart failure among others. It has been suggested that ACE inhibitors can reduce the symptoms in mouse models. Despite the benefits of ACE inhibitors, previous studies also have suggested that alterations in the ACE gene are risk factors for Alzheimer’s disease (AD) and other neurological diseases. In mice, overexpression of ACE in the brain reduces symptoms of the AD-model systems. Thus, we find opposing effects of ACE on health. To clarify the effects, we dissect the functions of ACE as follows: (1) angiotensin-converting enzyme that hydrolyzes angiotensin I to make angiotensin II in the renin-angiotensin system; (2) amyloid-degrading enzyme that can hydrolyze beta-amyloid and reduce amyloid toxicity. The efficacy of the ACE inhibitors is well established in humans, while the knowledge specific to AD remains to be open for further research. We provide an overview of ACE and inhibitors that link a wide variety of age-related comorbidities from hypertension to Alzheimer’s disease to aging. ACE also serves as an example of the middle-life crisis theory that assumes deleterious events during the midlife, leading to age-related later events.
ARTICLE | doi:10.20944/preprints201708.0031.v1
Subject: Keywords: cantilever; NiCr strain gauge; biosensor; liposome; amyloid beta; aggregation; fibrillization; interaction; human serum; digital low-pass filtering procedure
Online: 8 August 2017 (09:57:28 CEST)
We have successfully measured amyloid beta (Aβ) (1-40) protein added in human serum by a NiCr strain gauge cantilever biosensor immobilized with liposomes incorporating cholesterol. Importantly, we investigated the effect of incorporation of cholesterol in the liposome in order to suppress the interaction between the liposome and many different proteins included in human serum. It was revealed that incorporating cholesterol suppresses the interaction between the proteins other than Aβ in human serum and the liposome. Finally, we detected Aβ(1-40) in human serum with typical chronological behaviors due to Aβ aggregation and fibrillization. Furthermore, as a digital low-pass filtering procedure could reduce external noises, the cantilever sensor immobilized with liposome incorporating cholesterol can detect low-concentrated Aβ in human serum.
REVIEW | doi:10.20944/preprints202205.0166.v1
Subject: Life Sciences, Molecular Biology Keywords: Antimicrobial Peptides (AMPs); Alzheimer’s Disease (AD); infectious hypothesis; beta-amyloid (Ab); lactoferrin; defensins; cystatins; thymosin β4; histatin 1; statherin
Online: 12 May 2022 (09:40:33 CEST)
Alzheimer's Disease (AD) represents the most frequent type of dementia in elderly people. There are two major forms of the disease: sporadic (SAD) - whose causes are not completely understood - and familial (FAD) - with clear autosomal dominant inheritance. The two main hallmarks of AD are extracellular deposits of amyloid-beta (Ab) peptide and intracellular deposits of the hyperphosphorylated form of the tau protein (P-tau). An ever-growing body of research supports the infectious hypothesis of sporadic forms of AD. Indeed, it has been documented that some pathogens, such as herpesviruses and certain bacterial species, are commonly present in AD patients, prompting recent clinical research to focus on the characterization of Antimicrobial Peptides (AMPs) in this pathology. Literature also demonstrates that Ab can be considered itself as an AMP thus representing a type of innate immune defense peptide that protect the host against a variety of pathogens. Beyond Ab, other proteins with antimicrobial activity, such as lactoferrin, defensins, cystatins, thymosin β4, LL37, histatin 1 and statherin have been shown to be involved in AD. Here we have summarized and discussed these findings and explored the diagnostic and therapeutic potential of AMPs in AD.
ARTICLE | doi:10.20944/preprints202104.0270.v1
Subject: Chemistry, Analytical Chemistry Keywords: Systemic amyloidosis; amyloid fibrils; amyloidogenesis inhibitors; antibody light chains; light chain stabilizers; doxycycline; EGCG; thioflavin T; filter trap; PAINS
Online: 9 April 2021 (15:07:24 CEST)
Inhibition of amyloid fibril formation could benefit patients with systemic amyloidosis. In this group of diseases, deposition of amyloid fibrils derived from normally soluble proteins leads to progressive tissue damage and organ failure. Although many small molecules have been proposed as inhibitors of amyloid formation, few have been successful in clinical trials. Amyloid formation is complex and several individual steps could be targeted by small molecules. However, the exact mechanism of action for a molecule is often not known, which impedes medicinal chemistry efforts to develop more potent molecules. Furthermore, commonly used assays are prone to artifacts that must be controlled for. Here, potential mechanisms by which small molecules could inhibit aggregation of immunoglobulin light chain dimers, the precursor proteins for AL amyloidosis are studied in assays that recapitulate different aspects of amyloidogenesis in vitro. One molecule reduced unfolding-coupled proteolysis of light chains, but no molecules inhibited aggregation of light chains or disrupted pre-formed amyloid fibrils. This work demonstrates the challenges associated with drug development for amyloidosis, but also highlights the potential to combine therapies that target different aspects of amyloidogenesis.
REVIEW | doi:10.20944/preprints202101.0625.v1
Subject: Medicine & Pharmacology, Clinical Neurology Keywords: Alzheimer’s disease; dementia, beta-amyloid; germ theory; drug development; clinical trials; herpes; spirochetes; Chlamydia pneumoniae; Porphyromonas gingivalis; toxoplasma; mycobacteria
Online: 29 January 2021 (13:57:18 CET)
There is now considerable evidence that several infectious agents (viruses, bacteria, or parasites) may play a contributing role in the development of Alzheimer’s disease (AD). The six primary suspects are herpes viruses, spirochetal bacteria, Chlamydia pneumoniae, Porphyromonas gingivalis, mycobacteria, and toxoplasma parasites. Also, some of the antimicrobial and antiviral agents that are used to treat them have shown promise for AD interventions. I describe this evidence and assert it is now time to accelerate clinical trials of these existing drugs, already federally approved, to determine if such treatments can delay, halt, or reverse AD.
HYPOTHESIS | doi:10.20944/preprints202109.0437.v2
Subject: Life Sciences, Other Keywords: Alzheimer's; Cellular senescence; Neurodegeneration; Microglia; Astrocytes; Oligodendrocyte Progenitor Cells; TREM2; Braak staging; Oxidative stress; Phapoptosis; Amyloid-beta; Tau; Neuritic plaques
Online: 7 March 2022 (14:22:25 CET)
Alzheimer’s disease (AD) predominantly occurs as a late-onset form (LOAD), involving neurodegeneration and cognitive decline with progressive memory loss. Over time, risk factors and aging promote accumulation of well-known AD pathologies in oxidative stress, amyloid-beta and tau protein pathology, as well as inflammation. Homeostatic glial functions regulate and suppress these AD pathologies; however, other glial states involve increased pro-inflammatory cytokine release and further pathology accumulation. Different stresses can additionally induce cellular senescence, or an irreversible differentiation process resulting in decreased supportive functions and increased, pro-inflammatory cytokine release. While these pathophysiological underpinnings all contribute to LOAD, they require temporal and mechanistic integration. This perspective hypothesizes that when individuals have threshold senescent glia accumulation, they transition from healthy cognition into mild cognitive impairment and LOAD diagnosis. Particularly, senescent microglia are predicted to represent a final threshold required for the tau pathology burden and spreading that corresponds to sustained neurodegeneration and dementia severity. We first explore age-related decline in glia that promote increases in AD pathologies, and then discuss emerging evidence linking oxidative stress, neurons containing tau pathology, and amyloid-beta to microglia, oligodendrocyte progenitor cell, and astrocyte senescence. Our hypothesis proposes that senescent astrocytes and oligodendrocyte progenitors pressure microglia to phagocytose neurons containing tau pathology. The resulting senescent microglia would form neuritic plaques and induce paracrine senescence transitioning into a progressive clinical dementia presentation. This predictive hypothesis can potentially account for why medications used to treat LOAD fail, as previous treatments have not reduced senescent glial burden. It is also coherent with the predominant hypotheses surrounding LOAD, generates testable hypotheses about LOAD, and increases rationale in testing senolytics as targeted treatments for LOAD arrest and reversal.
REVIEW | doi:10.20944/preprints202110.0222.v1
Subject: Medicine & Pharmacology, Pharmacology & Toxicology Keywords: Alzheimer's disease; amyloid-beta; animal model; astrocyte; blood-brain barrier; imaging; metabolism; microglia; neuroinflammation, neurotransmitter receptors; positron emission tomography; synaptic density
Online: 15 October 2021 (11:02:57 CEST)
Animal models of Alzheimer’s disease amyloidosis that recapitulate cerebral amyloid-beta pathology have been widely used in preclinical research, and have greatly enabled the mechanistic understanding of Alzheimer’s disease and the development of therapeutics. Comprehensive deep phenotyping of the pathophysiological and biochemical features in these animal models are essential. Recent advances in positron emission tomography have allowed the non-invasive visualization of the alterations in the brain of animal models as well as in patients with Alzheimer’s disease, These tools have facilitated our understanding of disease mechanisms, and provided longitudinal monitoring of treatment effect in animal models of Alzheimer’s disease amyloidosis. In this review, we focus on recent positron emission tomography studies of cerebral amyloid-beta accumulation, hypoglucose metabolism, synaptic and neurotransmitter receptor deficits (cholinergic and glutamatergic system), blood-brain barrier impairment and neuroinflammation (microgliosis and astrocytosis) in animal models of Alzheimer’s disease amyloidosis. We further propose the emerging targets and tracers for reflecting the pathophysiological changes, and discuss outstanding challenges in disease animal models and future outlook in on-chip characterization of imaging biomarkers towards clinical translation.
REVIEW | doi:10.20944/preprints201802.0047.v1
Subject: Life Sciences, Biochemistry Keywords: Alzheimer disease; Amyloid β-protein; Antibodies; Cross-reactions; Nucleotide aptamers; Oligonucleotide ligands; Systematic evolution of ligands by exponential enrichment; Specificity; Therapeutics
Online: 5 February 2018 (22:37:02 CET)
Aptamers are versatile oligonucleotide ligands used for molecular recognition of diverse targets. However, application of aptamers to the field of amyloid β-protein (Aβ) has been limited so far. Aβ is an intrinsically disordered protein that exists in a dynamic conformational equilibrium, presenting time-dependent ensembles of short-lived, metastable structures and assemblies that have been generally difficult to isolate and characterize. Moreover, despite understanding of potential physiological roles of Aβ, this peptide has been linked to the pathogenesis of Alzheimer disease, and its pathogenic roles remain controversial. Accumulated scientific evidence thus far highlights undesirable or nonspecific interactions between selected aptamers and different Aβ assemblies likely due to metastable nature of Aβ or inherent affinity of RNA oligonucleotides to β-sheet-rich fibrillar structures of amyloidogenic proteins. Accordingly, lessons drawn from Aβ–aptamer studies emphasize that purity and uniformity of the protein target and rigorous characterization of aptamers’ specificity are important for realizing and garnering the full potential of aptamers selected for recongizing Aβ or other intrinsically disordered proteins. This review summarizes studies of aptamers selected for recognizing different Aβ assemblies and highlights controversies, difficulties, and limitations of such studies.
REVIEW | doi:10.20944/preprints201903.0108.v1
Subject: Life Sciences, Cell & Developmental Biology Keywords: Nucleolar sequestration, nucleolus, physiological amyloids, ribosomal intergenic spacer, rIGSRNA, liquid-liquid phase separation, liquid-to-solid phase transition, complex coacervation, biomolecular condensates, beta-amyloid, MDM2, VHL, Cdc14, low complexity RNA, acidosis, heat shock
Online: 8 March 2019 (15:12:29 CET)
This year marks the 20th anniversary of the discovery that proteins with various cellular functions can be temporarily immobilized in the nucleolus, a process known as nucleolar sequestration. This review reflects on the progress made to understand the physiological roles of nucleolar sequestration and the mechanisms involved in protein immobilization. We discuss how nucleolar sequestration consists of a highly choreographed amyloidogenic liquid-to-solid phase transition that converts the nucleolus into Amyloid bodies (A-bodies). The study of solid condensates A-bodies will offer unique perspectives on cellular assembly of membrane-less compartments and provide alternative insights on pathological amyloidogenesis involved in neurological disorders.