Unraveling the early events of amyloid-β protein (Aβ) aggregation: techniques for the determination of Aβ aggregate size

Nuclear pore dysfunction and disease: a complex opportunity

The separation of genetic material from bulk cytoplasm has enabled the evolution of increasingly complex organisms, allowing for the development of sophisticated forms of life. However, this complexity has created new categories of dysfunction, including those related to the movement of material between cellular compartments. In eukaryotic cells, nucleocytoplasmic trafficking is a fundamental biological process, and cumulative disruptions to nuclear integrity and nucleocytoplasmic transport are detrimental to cell survival. This is particularly true in post-mitotic neurons, where nuclear pore injury and errors to nucleocytoplasmic trafficking are strongly associated with neurodegenerative disease. In this review, we summarize the current understanding of nuclear pore biology in physiological and pathological contexts and discuss potential therapeutic approaches for addressing nuclear pore injury and dysfunctional nucleocytoplasmic transport.

Breaking Barriers in Alzheimer's Disease: the Role of Advanced Drug Delivery Systems

Alzheimer's disease (AD), characterized by cognitive impairment, brain plaques, and tangles, is a global health concern affecting millions. It involves the build-up of amyloid-β (Aβ) and tau proteins, the formation of neuritic plaques and neurofibrillary tangles, cholinergic system dysfunction, genetic variations, and mitochondrial dysfunction. Various signaling pathways and metabolic processes are implicated in AD, along with numerous biomarkers used for diagnosis, risk assessment, and research. Despite these, there is no cure or effective treatment for AD. It is critically important to address this immediately to develop novel drug delivery systems (NDDS) capable of targeting the brain and delivering therapeutic agents to modulate the pathological processes of AD. This review summarizes AD, its pathogenesis, related signaling pathways, biomarkers, conventional treatments, the need for NDDS, and their application in AD treatment. It also covers preclinical, clinical, and ongoing trials, patents, and marketed AD formulations.

Characterizing the Oligomers Distribution along the Aggregation Pathway of Amyloid Aβ1-40 by NMR

This study delves into the early aggregation process of the Aβ1-40 amyloid peptide, elucidating the associated oligomers distribution. Motivated by the acknowledged role of small oligomers in the neurotoxic damage linked to Alzheimer's disease, we present an experimental protocol for preparing 26-O-acyl isoAβ1-40, a modified Aβ1-40 peptide facilitating rapid isomerization to the native amide form at neutral pH. This ensures seed-free solutions, minimizing experimental variability. Additionally, we demonstrate the efficacy of coupling NMR diffusion ordered spectroscopy (DOSY) with the Inverse Laplace Transform (ILT) reconstruction method, for effective characterization of early aggregation processes. This innovative approach efficiently maps oligomers distributions across a wide spectrum of initial peptide concentrations offering unique insights into the evolution of oligomers relative populations. As a proof of concept, we demonstrate the efficacy of our approach assessing the impact of Epigallocathechin gallate, a known remodeling agent of amyloid fibrils, on the oligomeric distributions of aggregated Aβ1-40. The DOSY-ILT proposed approach stands as a robust and discriminating asset, providing a powerful strategy for rapidly gaining insight into potential inhibitors' impact on the aggregation process.

Targeting Amyloids with Coated Nanoparticles: A Review on Potential Combinations of Nanoparticles and Bio-Compatible Coatings

Amyloidosis is the major cause of many neurodegenerative diseases, such as, Alzheimer's and Parkinson's where the misfolding and deposition of a previously functional protein make it inept for carrying out its function. The genesis of amyloid fibril formation and the strategies to inhibit it have been studied extensively, although some parts of this puzzle still remain unfathomable to date. Many classes of molecules have been explored as potential drugs in vitro, but their inability to work in vivo by crossing the blood-brain-barrier has made them an inadequate treatment option. In this regard, nanoparticles (NPs) have turned out to be an exciting alternative because they could overcome many drawbacks of previously studied molecules and provide advantages, such as, greater bioavailability of molecules and target-specific delivery of drugs. In this paper, we present an overview on several coated NPs which have shown promising efficiency in inhibiting fibril formation. A hundred and thirty papers published in the past two decades have been comprehensively reviewed, which majorly encompass NPs comprising different materials like gold, silver, iron-oxide, poly(lactic-co-glycolic acid), polymeric NP, etc., which are coated with various molecules of predominantly natural origin, such as different types of amino acids, peptides, curcumin, drugs, catechin, etc. We hope that this review will shed light on the advancement of symbiotic amalgamation of NPs with molecules from natural sources and will inspire further research on the tremendous therapeutic potential of these combinations for many amyloid-related diseases.

Unveiling the Molecular Footprint: Proteome-Based Biomarkers for Alzheimer's Disease

Alzheimer's disease (AD) is a devastating neurodegenerative disorder characterized by progressive cognitive decline and memory loss. Early and accurate diagnosis of AD is crucial for implementing timely interventions and developing effective therapeutic strategies. Proteome-based biomarkers have emerged as promising tools for AD diagnosis and prognosis due to their ability to reflect disease-specific molecular alterations. There is of great significance for biomarkers in AD diagnosis and management. It emphasizes the limitations of existing diagnostic approaches and the need for reliable and accessible biomarkers. Proteomics, a field that comprehensively analyzes the entire protein complement of cells, tissues, or bio fluids, is presented as a powerful tool for identifying AD biomarkers. There is a diverse range of proteomic approaches employed in AD research, including mass spectrometry, two-dimensional gel electrophoresis, and protein microarrays. The challenges associated with identifying reliable biomarkers, such as sample heterogeneity and the dynamic nature of the disease. There are well-known proteins implicated in AD pathogenesis, such as amyloid-beta peptides, tau protein, Apo lipoprotein E, and clusterin, as well as inflammatory markers and complement proteins. Validation and clinical utility of proteome-based biomarkers are addressing the challenges involved in validation studies and the diagnostic accuracy of these biomarkers. There is great potential in monitoring disease progression and response to treatment, thereby aiding in personalized medicine approaches for AD patients. There is a great role for bioinformatics and data analysis in proteomics for AD biomarker research and the importance of data preprocessing, statistical analysis, pathway analysis, and integration of multi-omics data for a comprehensive understanding of AD pathophysiology. In conclusion, proteome-based biomarkers hold great promise in the field of AD research. They provide valuable insights into disease mechanisms, aid in early diagnosis, and facilitate personalized treatment strategies. However, further research and validation studies are necessary to harness the full potential of proteome-based biomarkers in clinical practice.

Chaperone Activity and Protective Effect against Aβ-Induced Cytotoxicity of Artocarpus camansi Blanco and Amaranthus dubius Mart. ex Thell Seed Protein Extracts

Alzheimer's disease (AD) is the most common type of dementia and is listed as the sixth-leading cause of death in the United States. Recent findings have linked AD to the aggregation of amyloid beta peptides (Aβ), a proteolytic fragment of 39-43 amino acid residues derived from the amyloid precursor protein. AD has no cure; thus, new therapies to stop the progression of this deadly disease are constantly being searched for. In recent years, chaperone-based medications from medicinal plants have gained significant interest as an anti-AD therapy. Chaperones are responsible for maintaining the three-dimensional shape of proteins and play an important role against neurotoxicity induced by the aggregation of misfolded proteins. Therefore, we hypothesized that proteins extracted from the seeds of Artocarpus camansi Blanco (A. camansi) and Amaranthus dubius Mart. ex Thell (A. dubius) could possess chaperone activity and consequently may exhibit a protective effect against Aβ_1-40-induced cytotoxicity. To test this hypothesis, the chaperone activity of these protein extracts was measured using the enzymatic reaction of citrate synthase (CS) under stress conditions. Then, their ability to inhibit the aggregation of Aβ_1-40 using a thioflavin T (ThT) fluorescence assay and DLS measurements was determined. Finally, the neuroprotective effect against Aβ_1-40 in SH-SY5Y neuroblastoma cells was evaluated. Our results demonstrated that A. camansi and A. dubius protein extracts exhibited chaperone activity and inhibited Aβ_1-40 fibril formation, with A. dubius showing the highest chaperone activity and inhibition at the concentration assessed. Additionally, both protein extracts showed neuroprotective effects against Aβ_1-40-induced toxicity. Overall, our data demonstrated that the plant-based proteins studied in this research work can effectively overcome one of the most important characteristics of AD.

Curcumin tautomerization in the mechanism of pentameric amyloid- β42 oligomers disassembly

Alzheimer's disease is a neurologic disorder characterized by the accumulation of extracellular deposits of amyloid-β (Aβ) fibrils in the brain of patients. The key etiologic agent in Alzheimer's disease is not known; however oligomeric Aβ appears detrimental to neuronal functions and increases Aβ fibrils deposition. Previous research has shown that curcumin, a phenolic pigment of turmeric, has an effect on Aβ assemblies, although the mechanism remains unclear. In this study, we demonstrate that curcumin disassembles pentameric oligomers made from synthetic Aβ42 peptides (pentameric oAβ42), using atomic force microscopy imaging followed by Gaussian analysis. Since curcumin shows keto-enol structural isomerism (tautomerism), the effect of keto-enol tautomerism on its disassembly was investigated. We have found that curcumin derivatives capable of keto-enol tautomerization also disassemble pentameric oAβ42, while, a curcumin derivative incapable of tautomerization did not affect the integrity of pentameric oAβ42. These experimental findings indicate that keto-enol tautomerism plays an essential role in the disassembly. We propose a mechanism for oAβ42 disassembly by curcumin based on molecular dynamics calculations of the tautomerism. When curcumin and its derivatives bind to the hydrophobic regions of oAβ42, the keto-form changes predominantly to the enol-form; this transition is associated with structural (twisting, planarization and rigidification) and potential energy changes that give curcumin enough force to act as a torsion molecular-spring that eventually disassembles pentameric oAβ42. This proposed mechanism sheds new light on keto-enol tautomerism as a relevant chemical feature for designing such novel therapeutic drugs that target protein aggregation.

Intracellular Amyloid-β Detection from Human Brain Sections Using a Microfluidic Immunoassay in Tandem with MALDI-MS

Alzheimer's disease (AD) currently affects more than 30 million people worldwide. The lack of understanding of AD's physiopathology limits the development of therapeutic and diagnostic tools. Soluble amyloid-β peptide (Aβ) oligomers that appear as intermediates along the Aβ aggregation into plaques are considered among the main AD neurotoxic species. Although a wealth of data are available about Aβ from in vitro and animal models, there is little known about intracellular Aβ in human brain cells, mainly due to the lack of technology to assess the intracellular protein content. The elucidation of the Aβ species in specific brain cell subpopulations can provide insight into the role of Aβ in AD and the neurotoxic mechanism involved. Here, we report a microfluidic immunoassay for in situ mass spectrometry analysis of intracellular Aβ species from archived human brain tissue. This approach comprises the selective laser dissection of individual pyramidal cell bodies from tissues, their transfer to the microfluidic platform for sample processing on-chip, and mass spectrometric characterization. As a proof-of-principle, we demonstrate the detection of intracellular Aβ species from as few as 20 human brain cells.

A review of the current research on in vivo and in vitro detection for alpha-synuclein: a biomarker of Parkinson's disease

Parkinson's disease is a health-threatening neurodegenerative disease of the elderly with clinical manifestations of motor and non-motor deficits such as tremor palsy and loss of smell. Alpha-synuclein (α-Syn) is the pathological basis of PD, it can abnormally aggregate into insoluble forms such as oligomers, fibrils, and plaques, causing degeneration of nigrostriatal dopaminergic neurons in the substantia nigra in the patient's brain and the formation of Lewy bodies (LBs) and Lewy neuritis (LN) inclusions. As a result, achieving α-Syn aggregate detection in the early stages of PD can effectively stop or delay the progression of the disease. In this paper, we provide a brief overview and analysis of the molecular structures and α-Syn in vivo and in vitro detection methods, such as mass spectrometry, antigen-antibody recognition, electrochemical sensors, and imaging techniques, intending to provide more technological support for detecting α-Syn early in the disease and intervening in the progression of Parkinson's disease.

Aβ8-20 Fragment as an Anti-Fibrillogenic and Neuroprotective Agent: Advancing toward Efficient Alzheimer's Disease Treatment

Alzheimer's disease (AD) is the most common cause of dementia, characterized by a spectrum of symptoms associated with memory loss and cognitive decline with deleterious consequences in everyday life. The lack of specific drugs for the treatment and/or prevention of this pathology makes AD an ever-increasing economic and social emergency. Oligomeric species of amyloid-beta (Aβ) are recognized as the primary cause responsible for synaptic dysfunction and neuronal degeneration, playing a crucial role in the onset of the pathology. Several studies have been focusing on the use of small molecules and peptides targeting oligomeric species to prevent Aβ aggregation and toxicity. Among them, peptide fragments derived from the primary sequence of Aβ have also been used to exploit any eventual recognition abilities toward the full-length Aβ parent peptide. Here, we test the Aβ_8-20 fragment which contains the self-recognizing Lys-Leu-Val-Phe-Phe sequence and lacks Arg 5 and Asp 7 and the main part of the C-terminus, key points involved in the aggregation pathway and stabilization of the fibrillary structure of Aβ. In particular, by combining chemical and biological techniques, we show that Aβ_8-20 does not undergo random coil to β sheet conformational transition, does not form amyloid fibrils by itself, and is not toxic for neuronal cells. Moreover, we demonstrate that Aβ_8-20 mainly interacts with the 4-11 region of Aβ_1-42 and inhibits the formation of toxic oligomeric species and Aβ fibrils. Finally, our data show that Aβ_8-20 protects neuron-like cells from Aβ_1-42 oligomer toxicity. We propose Aβ_8-20 as a promising drug candidate for the treatment of AD.

Solid-phase synthesis and pathological evaluation of pyroglutamate amyloid-β3-42 peptide

Pyroglutamate amyloid-β_3-42 (Aβ_pE3-42) is an N-terminally truncated and pyroglutamate-modified Aβ peptide retaining highly hydrophobic, amyloidogenic, and neurotoxic properties. In Alzheimer's disease (AD) patients, Aβ_pE3-42 peptides accumulate into oligomers and induce cellular toxicity and synaptic dysfunction. Aβ_pE3-42 aggregates further seed the formation of amyloid plaques, which are the pathological hallmarks of AD. Given that Aβ_pE3-42 peptides play critical roles in the development of neurodegeneration, a reliable and reproducible synthetic access to these peptides may support pathological and medicinal studies of AD. Here, we synthesized Aβ_pE3-42 peptides through the microwave-assisted solid-phase peptide synthesis (SPPS). Utilizing thioflavin T fluorescence assay and dot blotting analysis with anti-amyloid oligomer antibody, the amyloidogenic activity of synthesized Aβ_pE3-42 peptides was confirmed. We further observed the cytotoxicity of Aβ_pE3-42 aggregates in cell viability test. To examine the cognitive deficits induced by synthetic Aβ_pE3-42 peptides, Aβ_pE3-42 oligomers were intracerebroventricularly injected into imprinting control region mice and Y-maze and Morris water maze tests were performed. We found that Aβ_pE3-42 aggregates altered the expression level of postsynaptic density protein 95 in cortical lysates. Collectively, we produced Aβ_pE3-42 peptides in the microwave-assisted SPPS and evaluated the amyloidogenic and pathological function of the synthesized peptides.

The Influence of Selected Antipsychotic Drugs on Biochemical Aspects of Alzheimer's Disease

The aim of this study was to assess the potency of selected antipsychotic drugs (haloperidol (HAL), bromperidol (BRMP), benperidol (BNP), penfluridol (PNF), pimozide (PIM), quetiapine (QUET) and promazine (PROM)) on the main pathological hallmarks of Alzheimer's disease (AD). Binary mixtures of donepezil and antipsychotics produce an anti-BuChE effect, which was greater than either compound alone. The combination of rivastigmine and antipsychotic drugs (apart from PNF) enhanced AChE inhibition. The tested antipsychotics (excluding HAL and PNF) significantly reduce the early stage of Aβ aggregation. BRMP, PIM, QUET and PROM were found to substantially inhibit Aβ aggregation after a longer incubation time. A test of human erythrocytes hemolysis showed that short-term incubation of red blood cells (RBCs) with QUET resulted in decreased hemolysis. The antioxidative properties of antipsychotics were also proved in human umbilical vein endothelial cells (HUVEC); all tested drugs were found to significantly increase cell viability. In the case of astrocytes, BNP, PNF, PIM and PROM showed antioxidant potential.

Carnosic acid ameliorated Aβ-mediated (amyloid-β peptide) toxicity, cholinergic dysfunction and mitochondrial defect in Caenorhabditis elegans of Alzheimer's Model

Amyloid-β peptide (Aβ)-induced cholinergic system and mitochondrial dysfunction are major risk factors for Alzheimer's disease (AD). Our previous studies found that carnosic acid (CA), an important polyphenol antioxidant, could significantly delay Aβ_1-42-mediated acute paralysis. However, many details and underlying mechanisms of CA's neuroprotection against Aβ-induced cholinergic system defects and mitochondrial dysfunction remain unclear. Herein, we deeply investigated the effects and the possible mechanisms of CA-mediated protection against Aβ toxicity in vivo through several AD Caenorhabditis elegans strains. The results showed CA delayed age-related paralysis and Aβ deposition, and significantly protected neurons from Aβ-induced toxicity. CA might downgrade the expression of ace-1 and ace-2 genes, and upregulate cha-1 and unc-17 genes to inhibit acetylcholinesterase activity and relieve Aβ-caused cholinergic system defects. Furthermore, CA might also ameliorate Aβ-induced mitochondrial imbalance and oxidative stress through up-regulating the expression of phb-1, phb-2, eat-3, and drp-1 genes. The enhancements of the cholinergic system and mitochondrial function might be the reasons for the amelioration of Aβ-mediated toxicity and Aβ aggregation mediated by CA. These findings have helped us to understand the CA anti-Aβ activity in C. elegans and the potential mechanism of action.

Biological and methodological complexities of beta-amyloid peptide: Implications for Alzheimer's disease research

Although controversial, the amyloid cascade hypothesis remains central to the Alzheimer's disease (AD) field and posits amyloid-beta (Aβ) as the central factor initiating disease onset. In recent years, there has been an increase in emphasis on studying the role of low molecular weight aggregates, such as oligomers, which are suggested to be more neurotoxic than fibrillary Aβ. Other Aβ isoforms, such as truncated Aβ, have also been implicated in disease. However, developing a clear understanding of AD pathogenesis has been hampered by the complexity of Aβ biochemistry in vitro and in vivo. This review explores factors contributing to the lack of consistency in experimental approaches taken to model Aβ aggregation and toxicity and provides an overview of the different techniques available to analyse Aβ, such as electron and atomic force microscopy, nuclear magnetic resonance spectroscopy, dye-based assays, size exclusion chromatography, mass spectrometry and SDS-PAGE. The review also explores how different types of Aβ can influence Aβ aggregation and toxicity, leading to variation in experimental outcomes, further highlighting the need for standardisation in Aβ preparations and methods used in current research.

Alzheimer's Aβ assembly binds sodium pump and blocks endothelial NOS activity via ROS-PKC pathway in brain vascular endothelial cells

Amyloid β-protein (Aβ) may contribute to worsening of Alzheimer's disease (AD) through vascular dysfunction, but the molecular mechanism involved is unknown. Using ex vivo blood vessels and primary endothelial cells from human brain microvessels, we show that patient-derived Aβ assemblies, termed amylospheroids (ASPD), exist on the microvascular surface in patients' brains and inhibit vasorelaxation through binding to the α3 subunit of sodium, potassium-ATPase (NAKα3) in caveolae on endothelial cells. Interestingly, NAKα3 is also the toxic target of ASPD in neurons. ASPD-NAKα3 interaction elicits neurodegeneration through calcium overload in neurons, while the same interaction suppresses vasorelaxation by increasing the inactive form of endothelial nitric oxide synthase (eNOS) in endothelial cells via mitochondrial ROS and protein kinase C, independently of the physiological relaxation system. Thus, ASPD may contribute to both neuronal and vascular pathologies through binding to NAKα3. Therefore, blocking the ASPD-NAKα3 interaction may be a useful target for AD therapy.

In Vitro Biosensing of β-Amyloid Peptide Aggregation Dynamics using a Biological Nanopore

Alzheimer's disease and other neurodegenerative disorders are becoming more prevalent as advances in technology and medicine increase living standards and life expectancy. Alzheimer's disease is thought to initiate development early in the patient's life and progresses continuously into old age. This process is characterized molecularly by the amyloid hypothesis, which asserts that self-aggregating amyloid peptides are core to the pathophysiology in Alzheimer's progression. Precise quantification of amyloid peptides in human bodily fluid samples (i.e. cerebrospinal fluid, blood) may inform diagnosis and prognosis, and has been studied using established biosensing technologies like liquid chromatography, mass spectrometry, and immunoassays. However, existing methods are challenged to provide single molecule, quantitative analysis of the disease-causing aggregation process. Ultra-sensitive nanopore biosensors can step in to fill this role as a dynamic mapping tool. The work in this paper establishes characteristic signals of β-amyloid 40 monomers, oligomers, and soluble aggregates, as well as a proof-of-concept foundation where a biological nanopore biosensor is used to monitor the extent of in vitro β-amyloid 40 peptide aggregation at the single molecule level. This foundation allows for future work to expand in drug screening, diagnostics, and aggregation dynamic experiments.

Beneficial Effects of Cyclic Ether 2-Butoxytetrahydrofuran from Sea Cucumber Holothuria scabra against Aβ Aggregate Toxicity in Transgenic Caenorhabditis elegans and Potential Chemical Interaction

The pathological finding of amyloid-β (Aβ) aggregates is thought to be a leading cause of untreated Alzheimer’s disease (AD). In this study, we isolated 2-butoxytetrahydrofuran (2-BTHF), a small cyclic ether, from Holothuria scabra and demonstrated its therapeutic potential against AD through the attenuation of Aβ aggregation in a transgenic Caenorhabditis elegans model. Our results revealed that amongst the five H. scabra isolated compounds, 2-BTHF was shown to be the most effective in suppressing worm paralysis caused by Aβ toxicity and in expressing strong neuroprotection in CL4176 and CL2355 strains, respectively. An immunoblot analysis showed that CL4176 and CL2006 treated with 2-BTHF showed no effect on the level of Aβ monomers but significantly reduced the toxic oligomeric form and the amount of 1,4-bis(3-carboxy-hydroxy-phenylethenyl)-benzene (X-34)-positive fibril deposits. This concurrently occurred with a reduction of reactive oxygen species (ROS) in the treated CL4176 worms. Mechanistically, heat shock factor 1 (HSF-1) (at residues histidine 63 (HIS63) and glutamine 72 (GLN72)) was shown to be 2-BTHF’s potential target that might contribute to an increased expression of autophagy-related genes required for the breakdown of the Aβ aggregate, thus attenuating its toxicity. In conclusion, 2-BTHF from H. scabra could protect C. elegans from Aβ toxicity by suppressing its aggregation via an HSF-1-regulated autophagic pathway and has been implicated as a potential drug for AD.

Quantifying misfolded protein oligomers as drug targets and biomarkers in Alzheimer and Parkinson diseases

Protein misfolding and aggregation are characteristic of a wide range of neurodegenerative disorders, including Alzheimer and Parkinson diseases. A hallmark of these diseases is the aggregation of otherwise soluble and functional proteins into amyloid aggregates. Although for many decades such amyloid deposits have been thought to be responsible for disease progression, it is now increasingly recognized that the misfolded protein oligomers formed during aggregation are, instead, the main agents causing pathological processes. These oligomers are transient and heterogeneous, which makes it difficult to detect and quantify them, generating confusion about their exact role in disease. The lack of suitable methods to address these challenges has hampered efforts to investigate the molecular mechanisms of oligomer toxicity and to develop oligomer-based diagnostic and therapeutic tools to combat protein misfolding diseases. In this Review, we describe methods to quantify misfolded protein oligomers, with particular emphasis on diagnostic applications as disease biomarkers and on therapeutic applications as target biomarkers. The development of these methods is ongoing, and we discuss the challenges that remain to be addressed to establish measurement tools capable of overcoming existing limitations and to meet present needs.

Low frequency vortex magnetic field reduces amyloid β aggregation, increase cell viability and protect from amyloid β toxicity

Plaques formed by abnormal accumulation of amyloid β-peptide (Aβ) lead to onset of Alzheimer's disease (AD). Pharmacological treatments do not reduce Aβ aggregation neither restore learning and memory. Noninvasive techniques have emerged as an alternative to treat AD, such as stimulation with electromagnetic fields (EMF) that decrease Aβ deposition and reverses cognitive impairment in AD mice, even though some studies showed side effects on parallel magnetic fields stimulation. As a new approach of magnetic field (MF) stimulation, vortex magnetic fields (VMF) have been tested inducing a random movement of charged biomolecules in cells, promoting cell viability and apparently safer than parallel magnetic fields. In this study we demonstrate the effect of VMF on Aβ aggregation. The experimental strategy includes, i) design and construction of a coil capable to induce VMF, ii) evaluation of VMF stimulation on Aβ peptide induced-fibrils-formation, iii) evaluation of VMF stimulation on SH-SY5Y neuroblastoma cell line in the presence of Aβ peptide. We demonstrated for the first time that Aβ aggregation exposed to VMF during 24 h decreased ~ 86% of Aβ fibril formation compared to control. Likewise, VMF stimulation reduced Aβ fibrils-cytotoxicity and increase SH-SY5Y cell viability. These data establish the basis for future investigation that involve VMF as inhibitor of Aβ-pathology and indicate the therapeutic potential of VMF for AD treatment.

Multispectral Nanoparticle Tracking Analysis for the Real-Time and Label-Free Characterization of Amyloid-β Self-Assembly In Vitro

The deposition of amyloid β (Aβ) plaques and fibrils in the brain parenchyma is a hallmark of Alzheimer's disease (AD), but a mechanistic understanding of the role Aβ plays in AD has remained unclear. One important reason could be the limitations of current tools to size and count Aβ fibrils in real time. Conventional techniques from molecular biology largely use ensemble averaging; some microscopy analyses have been reported but suffer from low throughput. Nanoparticle tracking analysis is an alternative approach developed in the past decade for sizing and counting particles according to their Brownian motion; however, it is limited in sensitivity to polydisperse solutions because it uses only one laser. More recently, multispectral nanoparticle tracking analysis (MNTA) was introduced to address this limitation; it uses three visible wavelengths to quantitate heterogeneous particle distributions. Here, we used MNTA as a label-free technique to characterize the in vitro kinetics of Aβ1-42 aggregation by measuring the size distributions of aggregates during self-assembly. Our results show that this technology can monitor the aggregation of 106-108 particles/mL with a temporal resolution between 15 and 30 min. We corroborated this method with the fluorescent Thioflavin-T assay and transmission electron microscopy (TEM), showing good agreement between the techniques (Pearson's r = 0.821, P < 0.0001). We also used fluorescent gating to examine the effect of ThT on the aggregate size distribution. Finally, the biological relevance was demonstrated via fibril modulation in the presence of a polyphenolic Aβ disruptor. In summary, this approach measures Aβ assembly similar to ensemble-type measurements but with per-fibril resolution.

Cotinine and 6-Hydroxy-L-Nicotine Reverses Memory Deficits and Reduces Oxidative Stress in Aβ25-35-Induced Rat Model of Alzheimer's Disease

The nicotinic derivatives, cotinine (COT), and 6-hydroxy-L-nicotine (6HLN), showed promising cognitive-improving effects without exhibiting the nicotine's side-effects. Here, we investigated the impact of COT and 6HLN on memory impairment and the oxidative stress in the Aβ25-35-induced rat model of Alzheimer's disease (AD). COT and 6HLN were chronically administered to Aβ25-35-treated rats, and their memory performances were assessed using in vivo tasks (Y-maze, novel object recognition, and radial arm maze). By using in silico tools, we attempted to associate the behavioral outcomes with the calculated binding potential of these nicotinic compounds in the allosteric sites of α7 and α4β2 subtypes of the nicotinic acetylcholine receptors (nAChRs). The oxidative status and acetylcholinesterase (AChE) activity were determined from the hippocampal tissues. RT-qPCR assessed bdnf, arc, and il-1β mRNA levels. Our data revealed that COT and 6HLN could bind to α7 and α4β2 nAChRs with similar or even higher affinity than nicotine. Consequently, the treatment exhibited a pro-cognitive, antioxidant, and anti-AChE profile in the Aβ25-35-induced rat model of AD. Finally, RT-qPCR analysis revealed that COT and 6HLN positively modulated the bdnf, arc, and il-1β genes expression. Therefore, these nicotinic derivatives that act on the cholinergic system might represent a promising choice to ameliorate AD conditions.

Shear-induced aggregation of amyloid β (1-40) in a parallel plate geometry

Protein aggregation is induced by various environmental or external factors and associated with various neurodegenerative diseases. Among various external factors, shear stress is inevitable for both in vivo and in vitro applications of proteins. In this study, Aβ (1-40) peptide, a derivative of the amyloid precursor protein, was subjected to constant (300, 500, 700 s^-1) and varying (ramp) shear in a parallel plate geometry to explore the implications of shear in terms of macro (viscosity) and micro (secondary structure, morphology) characteristics. Aβ (1-40) solution followed a shear thickening flow behaviour with performance index value 'n' of 2.12. The fibrillation process resulting from the shear force was evaluated in terms of dissipation energy, which was found to exceed the free energy of unfolding. This resulted in the formation of β-sheet rich structures, which were confirmed by CD and FTIR analyses and enhanced Th-T fluorescence. The apparent rate of aggregation (k) was found to increase with the shear rate, and inversely related to the solution viscosity. The maximum k value was 0.21 ± 0.3 min^-1 at 700 s^-1. The molecular weights of aggregates were determined using gel filtration, which were proportionally related to the solution viscosity. The average molecular weights were estimated to be 70, 62 and 52 KDa for samples sheared at 300, 500 and 700 s^-1, respectively. The present study has deciphered the interplay of viscosity, a fluid property, with the aggregation process and its corresponding change in the secondary structures of the peptide. These findings provide useful insights for understanding various proteopathies under shear force.Communicated by Ramaswamy H. Sarma.

A Three-Dimensional Alzheimer's Disease Cell Culture Model Using iPSC-Derived Neurons Carrying A246E Mutation in PSEN1

Alzheimer's disease (AD) is a chronic brain disorder characterized by progressive intellectual decline and memory and neuronal loss, caused mainly by extracellular deposition of amyloid-β (Aβ) and intracellular accumulation of hyperphosphorylated tau protein, primarily in areas implicated in memory and learning as prefrontal cortex and hippocampus. There are two forms of AD, a late-onset form that affects people over 65 years old, and the early-onset form, which is hereditable and affect people at early ages ~45 years. To date, there is no cure for the disease; consequently, it is essential to develop new tools for the study of processes implicated in the disease. Currently, in vitro AD three-dimensional (3D) models using induced pluripotent stem cells (iPSC)-derived neurons have broadened the horizon for in vitro disease modeling and gained interest for mechanistic studies and preclinical drug discovery due to their potential advantages in providing a better physiologically relevant information and more predictive data for in vivo tests. Therefore, this study aimed to establish a 3D cell culture model of AD in vitro using iPSCs carrying the A246E mutation. We generated human iPSCs from fibroblasts from a patient with AD harboring the A246E mutation in the PSEN1 gene. Cell reprogramming was performed using lentiviral vectors with Yamanaka's factors (OSKM: Oct4, Sox2, Klf4, and c-Myc). The resulting iPSCs expressed pluripotency genes (such as Nanog and Oct4), alkaline phosphatase activity, and pluripotency stem cell marker expression, such as OCT4, SOX2, TRA-1-60, and SSEA4. iPSCs exhibited the ability to differentiate into neuronal lineage in a 3D environment through dual SMAD inhibition as confirmed by Nestin, MAP2, and Tuj1 neural marker expression. These iPSC-derived neurons harbored Aβ oligomers confirmed by Western Blot (WB) and immunostaining. With human iPSC-derived neurons able to produce Aβ oligomers, we established a novel human hydrogel-based 3D cell culture model that recapitulates Aβ aggregation without the need for mutation induction or synthetic Aβ exposure. This model will allow the study of processes implicated in disease spread throughout the brain, the screening of molecules or compounds with therapeutic potential, and the development of personalized therapeutic strategies.

Advances in Studies on Stroke-Induced Secondary Neurodegeneration (SND) and Its Treatment

Background:

The occurrence of secondary neurodegeneration has exclusively been observed after the first incidence of stroke. In humans and rodents, post-stroke secondary neurodegeneration (SND) is an inevitable event that can lead to progressive neuronal loss at a region distant to initial infarct. SND can lead to cognitive and motor function impairment, finally causing dementia. The exact pathophysiology of the event is yet to be explored. It is seen that the thalami, in particular, are susceptible to cause SND. The reason behind this is because the thalamus functioning as the relay center and is positioned as an interlocked structure with direct synaptic signaling connection with the cortex. As SND proceeds, accumulation of misfolded proteins and microglial activation are seen in the thalamus. This leads to increased neuronal loss and worsening of functional and cognitive impairment.

Objective:

There is a necessity of specific interventions to prevent post-stroke SND, which are not properly investigated to date owing to sparsely reproducible pre-clinical and clinical data. The basis of this review is to investigate about post-stroke SND and its updated treatment approaches carefully.

Methods:

Our article presents a detailed survey of advances in studies on stroke-induced secondary neurodegeneration (SND) and its treatment.

Results:

This article aims to put forward the pathophysiology of SND. We have also tabulated the latest treatment approaches along with different neuroimaging systems that will be helpful for future reference to explore.

Conclusion:

In this article, we have reviewed the available reports on SND pathophysiology, detection techniques, and possible treatment modalities that have not been attempted to date.

Humanin Blocks the Aggregation of Amyloid-β Induced by Acetylcholinesterase, an Effect Abolished in the Presence of IGFBP-3

It is known that the humanin (HN) peptide binding to amyloid-β (Aβ) protects against its cytotoxic effects, while acetylcholinesterase (AChE) binding to Aβ increases its aggregation and cytotoxicity. HN is also known to bind the insulin-like growth factor binding protein-3 (IGFBP-3). Here, we examined the regulation of Aβ conformations by HN, AChE, and IGFBP-3 both in vitro and in the conditioned media from A549 and H1299 lung cancer cells. Our in vitro results showed the following: IGFBP-3 binds HN and blocks it from binding Aβ in the absence or presence of AChE; HN and AChE can simultaneously bind Aβ but not when in the presence of IGFBP-3; HN is unable to reduce the aggregation of Aβ in the presence of IGFBP-3; and HN abolishes the aggregation of Aβ induced by the addition of AChE in the absence of IGFBP-3. In the media, AChE and HN can simultaneously bind Aβ. While both AChE and HN are detected when using 6E10 Aβ antibodies, only AChE is detected when using the Aβ 17-24 antibody 4G8, the anti-oligomer A11, and the anti-amyloid fibril LOC antibodies. No signal was observed for IGFBP-3 with any of the anti-amyloid antibodies used. Exogenously added IGFBP-3 reduced the amount of HN found in a complex when using 6E10 antibodies and correlated with a concomitant increase in the amyloid oligomers. Immunodepletion of HN from the media of the A549 and H1299 cells increased the relative abundance of the oligomer vs the total amount of Aβ, the A11-positive prefibrillar oligomers, and to a lesser extent the LOC-positive fibrillar oligomers, and was also correlated with diminished cell viability and increased apoptosis.

Effects of Cholesterol in Stress-Related Neuronal Death-A Statistical Analysis Perspective

The association between plasma cholesterol levels and the development of dementia continues to be an important topic of discussion in the scientific community, while the results in the literature vary significantly. We study the effect of reducing oxidized neuronal cholesterol on the lipid raft structure of plasma membrane. The levels of plasma membrane cholesterol were reduced by treating the intact cells with methyl-ß-cyclodextrin (MßCD). The relationship between the cell viability with varying levels of MßCD was then examined. The viability curves are well described by a modified form of the empirical Gompertz law of mortality. A detailed statistical analysis is performed on the fitting results, showing that increasing MßCD concentration has a minor, rather than significant, effect on the cellular viability. In particular, the dependence of viability on MßCD concentration was found to be characterized by a ~25% increase per 1 μM of MßCD concentration.

Acetylation of Aβ42 at Lysine 16 Disrupts Amyloid Formation

The residue lysine 28 (K28) is known to form an important salt bridge that stabilizes the Aβ amyloid structure, and acetylation of lysine 28 (K28Ac) slows the Aβ42 fibrillization rate but does not affect fibril morphology. On the other hand, acetylation of lysine 16 (K16Ac) residue greatly diminishes the fibrillization property of Aβ42 peptide and also affects its toxicity. This is due to the fact that lysine 16 acetylated amyloid beta peptide forms amorphous aggregates instead of amyloid fibrils. This is likely a result of increased hydrophobicity of the K16-A21 region due to K16 acetylation, as confirmed by molecular dynamic simulation studies. The calculated results show that the hydrophobic patches of aggregates from acetylated peptides were different when compared to wild-type (WT) peptide. K16Ac and double acetylated (KKAc) peptide aggregates show significantly higher cytotoxicity compared to the WT or K28Ac peptide aggregates alone. However, the heterogeneous mixture of WT and acetylated Aβ42 peptide aggregates exhibited higher free radical formation as well as cytotoxicity, suggesting dynamic interactions between different species could be a critical contributor to Aβ pathology.

Medroxyprogesterone Acetate Impairs Amyloid Beta Degradation in a Matrix Metalloproteinase-9 Dependent Manner

Despite the extensive use of hormonal methods as either contraception or menopausal hormone therapy (HT), there is very little known about the potential effects of these compounds on the cellular processes of the brain. Medroxyprogesterone Acetate (MPA) is a progestogen used globally in the hormonal contraceptive, Depo Provera, by women in their reproductive prime and is a major compound found in HT formulations used by menopausal women. MPA promotes changes in the circulating levels of matrix metalloproteinases (MMPs), such as MMP-9, in the endometrium, yet limited literature studying the effects of MPA on neurons and astroglia cells has been conducted. Additionally, the dysregulation of MMPs has been implicated in the pathology of Alzheimer's disease (AD), where inhibiting the secretion of MMP-9 from astroglia reduces the proteolytic degradation of amyloid-beta. Thus, we hypothesize that exposure to MPA disrupts proteolytic degradation of amyloid-beta through the downregulation of MMP-9 expression and subsequent secretion. To assess the effect of progestins on MMP-9 and amyloid-beta, in vitro, C6 rat glial cells were exposed to MPA for 48 h and then the enzymatic, secretory, and amyloid-beta degrading capacity of MMP-9 was assessed from the conditioned culture medium. We found that MPA treatment inhibited transcription of MMP-9, which resulted in a subsequent decrease in the production and secretion of MMP-9 protein, in part through the glucocorticoid receptor. Additionally, we investigated the consequences of amyloid beta-degrading activity and found that MPA treatment decreased proteolytic degradation of amyloid-beta. Our results suggest MPA suppresses amyloid-beta degradation in an MMP-9-dependent manner, in vitro, and potentially compromises the clearance of amyloid-beta in vivo.

Complete aggregation pathway of amyloid β (1-40) and (1-42) resolved on an atomically clean interface

To visualize amyloid β (Aβ) aggregates requires an uncontaminated and artifact-free interface. This paper demonstrates the interface between graphene and pure water (verified to be atomically clean using tunneling microscopy) as an ideal platform for resolving size, shape, and morphology (measured by atomic force microscopy) of Aβ-40 and Aβ-42 peptide assemblies from 0.5 to 150 hours at a 5-hour time interval with single-particle resolution. After confirming faster aggregation of Aβ-42 in comparison to Aβ-40, a stable set of oligomers with a diameter distribution of ~7 to 9 nm was prevalently observed uniquely for Aβ-42 even after fibril appearance. The interaction energies between a distinct class of amyloid aggregates (dodecamers) and graphene was then quantified using molecular dynamics simulations. Last, differences in Aβ-40 and Aβ-42 networks were resolved, wherein only Aβ-42 fibrils were aligned through lateral interactions over micrometer-scale lengths, a property that could be exploited in the design of biofunctional materials.

A novel role for SHARPIN in amyloid-β phagocytosis and inflammation by peripheral blood-derived macrophages in Alzheimer's disease

Defective immune cell-mediated clearance of amyloid-beta (Aβ) and Aβ-associated inflammatory activation of immune cells are key contributors in pathogenesis of Alzheimer's disease (AD). However, the underlying mechanisms remain elusive. Shank-associated RH domain-interacting protein (SHARPIN) is a critical regulator of inflammatory response. Using in vitro cultures of THP-1-derived macrophages exposed to Aβ and AD patient-derived macrophages, we demonstrate the role of SHARPIN as an obligate regulator of Aβ phagocytosis and inflammation in macrophages. Specifically, Aβ-stimulated SHARPIN in THP-1 macrophages promoted Aβ phagocytosis and expression of proinflammatory markers. In addition, Aβ-stimulated SHARPIN in macrophages promoted neuronal cell-death in differentiated SHSY5Y neurons. Furthermore, we report a novel regulatory link between SHARPIN and the NLRP3 inflammasome in response to Aβ in THP-1 macrophages. In line with our in vitro observations, a strong positive association was demonstrated between levels of Aβ₄₂ in blood plasma of mild cognitive impairment and AD patients with SHARPIN expression in macrophages obtained from respective patient-derived peripheral blood mononuclear cells. Together, our findings show SHARPIN as a critical determinant in mediating macrophage response to Aβ and pathogenesis of AD.

Investigating the interactions of the first 17 amino acid residues of Huntingtin with lipid vesicles using mass spectrometry and molecular dynamics

The first 17 amino acid residues of Huntingtin protein (Nt17 of htt) are thought to play an important role in the protein's function; Nt17 is one of two membrane binding domains in htt. In this study the binding ability of Nt17 peptide with vesicles comprised of two subclasses of phospholipids is studied using electrospray ionization - mass spectrometry (ESI-MS) and molecular dynamics (MD) simulations. Overall, the peptide is shown to have a greater propensity to interact with vesicles of phosphatidylcholine (PC) rather than phosphatidylethanolamine (PE) lipids. Mass spectra show an increase in lipid-bound peptide adducts where the ordering of the number of such specie is 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) > 1-palmitoyl-2-oleoyl-glycero-3-phosphocholine (POPC) > 1-palmitoyl-2-oleoyl-sn-glycero-3 phosphoethanolamine (POPE). MD simulations suggest that the compactness of the bilayer plays a role in governing peptide interactions. The peptide shows greater disruption of the DOPC bilayer order at the surface and interacts with the hydrophobic tails of lipid molecules via hydrophobic residues. Conversely, the POPE vesicle remains ordered and lipids display transient interactions with the peptide through the formation of hydrogen bonds with hydrophilic residues. The POPC system displays intermediate behavior with regard to the degree of peptide-membrane interaction. Finally, the simulations suggest a helix stabilizing effect resulting from the interactions between hydrophobic residues and the lipid tails of the DOPC bilayer.

Amyloid-β induced neuropathological actions are suppressed by Padina gymnospora (Phaeophyceae) and its active constituent α-bisabolol in Neuro2a cells and transgenic Caenorhabditis elegans Alzheimer's model

The inhibition of Aβ peptide development and aggregation is a hopeful curative approach for the discovery of disease modifying drugs for Alzheimer's disease (AD) treatment. Recent research mainly focuses on the discovery of drugs from marine setting due to their immense therapeutic potential. The present study aims to evaluate the brown macroalga Padina gymnospora and its active constituent α-bisabolol against Aβ25-35 induced neurotoxicity in Neuro2a cells and transgenic Caenorhabditis elegans (CL2006 and CL4176). The results of the in vitro study revealed that the acetone extract of P. gymnospora (ACTPG) and its active constituent α-bisabolol restores the Aβ25-35 induced alteration in the oxidation of intracellular protein and lipids. In addition, ACTPG and α-bisabolol inhibited cholinesterase and β-secretase activity in Neuro2a cells. Moreover, the intracellular reactive oxygen species (ROS) and reactive nitrogen species (RNS) production was reduced by ACTPG and α-bisabolol in Neuro2a cells. The decrease in the expression level of apoptotic proteins such as Bax and caspase-3 in ACTPG and α-bisabolol treated group indicates that the seaweed and its bioactive compound have anti-apoptotic property. Further, the in vivo study revealed that the ACTPG and α-bisabolol exerts neuroprotective effect against Aβ induced proteotoxicity in transgenic C. elegans strains of AD. Moreover it altered the Aβ mediated pathways, lifespan, macromolecular damage and down regulated the AD related gene expression of ace-1, hsp-4 and Aβ, thereby preventing Aβ synthesis. Overall, the outcome of the study signifies the neuroprotective effect of ACTPG and α-bisabolol against Aβ mediated AD pathology.

Glycosylated amyloid-like proteins in the structural extracellular polymers of aerobic granular sludge enriched with ammonium-oxidizing bacteria

A new type of structural extracellular polymers (EPS) was extracted from aerobic granular sludge dominated by ammonium-oxidizing bacteria. It was analyzed by Raman and FTIR spectroscopy to characterize specific amino acids and protein secondary structure, and by SDS-PAGE with different stains to identify different glycoconjugates. Its intrinsic fluorescence was captured to visualize the location of the extracted EPS in the nitrifying granules, and its hydrogel-forming property was studied by rheometry. The extracted EPS is abundant with cross ß-sheet secondary structure, contains glycosylated proteins/polypeptides, and rich in tryptophan. It forms hydrogel with high mechanical strength. The extraction and discovery of glycosylated proteins and/or amyloids further shows that conventionally used extraction and characterization techniques are not adequate for the study of structural extracellular polymers in biofilms and/or granular sludge. Confirming amyloids secondary structure in such a complex sample is challengeable due to the possibility of amyloids glycosylation and self-assembly. A new definition of extracellular polymers components which includes glycosylated proteins and a better approach to studying them is required to stimulate biofilm research.

A pyrene-inhibitor fluorescent probe with large Stokes shift for the staining of Aβ1-42, α-synuclein, and amylin amyloid fibrils as well as amyloid-containing Staphylococcus aureus biofilms

Amyloid fibrils formed by a variety of peptides are biological markers of different human diseases, such as Alzheimer's disease, Parkinson's disease, and type II diabetes, and are structural constituents of bacterial biofilms. Novel fluorescent probes offering improved sensitivity or specificity toward that diversity of amyloid fibrils or providing alternative spectral windows are needed to improve the detection or the identification of amyloid structures. One potential source for such new probes is offered by molecules known to interact with fibrils, such as the inhibitors of amyloid aggregation found in drug discovery projects. Here we show the feasibility of the approach by designing, synthesizing, and testing several pyrene-based fluorescent derivatives of a previously discovered inhibitor of the aggregation of the Aβ_1-42 peptide. All the derivatives tested retain the interaction with the amyloid architecture and allow its staining. The most soluble derivative, N-acetyl-2-(2-methyl-4-oxo-5,6,7,8-tetrahydro-4H-benzo[4,5]thieno[2,3-d][1,3]oxazin-7-yl)-N-(pyren-1-ylmethyl)acetamide (compound 1D), stains similarly well amyloid fibrils formed by Aβ_1-42, α-synuclein, or amylin, provides a sensitivity only slightly lower than that of thioflavin T, displays a large Stokes shift, allows efficient excitation in the UV spectral region, and is not cytotoxic. Compound 1D can also stain amyloid fibrils formed by staphylococcal peptides present in biofilm matrices and can be used to distinguish, by direct staining, Staphylococcus aureus biofilms containing amyloid-forming phenol-soluble modulins from those lacking them. Graphical abstract ᅟ.

Recent Advances by In Silico and In Vitro Studies of Amyloid-β 1-42 Fibril Depicted a S-Shape Conformation

The amyloid-β 1-42 (Aβ1-42) peptide is produced by proteolytic cleavage of the amyloid precursor protein (APP) by sequential reactions that are catalyzed by γ and β secretases. Aβ1-42, together with the Tau protein are two principal hallmarks of Alzheimer's disease (AD) that are related to disease genesis and progression. Aβ1-42 possesses a higher aggregation propensity, and it is able to form fibrils via nucleated fibril formation. To date, there are compounds available that prevent Aβ1-42 aggregation, but none have been successful in clinical trials, possibly because the Aβ1-42 structure and aggregation mechanisms are not thoroughly understood. New molecules have been designed, employing knowledge of the Aβ1-42 structure and are based on preventing or breaking the ionic interactions that have been proposed for formation of the Aβ1-42 fibril U-shaped structure. Recently, a new Aβ1-42 fibril S-shaped structure was reported that, together with its aggregation and catalytic properties, could be helpful in the design of new inhibitor molecules. Therefore, in silico and in vitro methods have been employed to analyze the Aβ1-42 fibril S-shaped structure and its aggregation to obtain more accurate Aβ1-42 oligomerization data for the design and evaluation of new molecules that can prevent the fibrillation process.

A discrete mathematical model for the aggregation of β-Amyloid

Dementia associated with the Alzheimer's disease is thought to be correlated with the conversion of the β − Amyloid (Aβ) peptides from soluble monomers to aggregated oligomers and insoluble fibrils. We present a discrete-time mathematical model for the aggregation of Aβ monomers into oligomers using concepts from chemical kinetics and population dynamics. Conditions for the stability and instability of the equilibria of the model are established. A formula for the number of monomers that is required for producing oligomers is also given. This may provide compound designers a mechanism to inhibit the Aβ aggregation.

Detection of Amyloid Beta (Aβ) Oligomeric Composition Using Matrix-Assisted Laser Desorption Ionization Mass Spectrometry (MALDI MS)

The use of MALDI MS as a fast and direct method to detect the Aβ oligomers of different masses is examined in this paper. Experimental results suggest that Aβ oligomers are ionized and detected as singly charged ions, and thus, the resulting mass spectrum directly reports the oligomer size distribution. Validation experiments were performed to verify the MS data against artifacts. Mass spectra collected from modified Aβ peptides with different propensities for aggregation were compared. Generally, the relative intensities of multimers were higher from samples where oligomerization was expected to be more favorable, and vice versa. MALDI MS was also able to detect the differences in oligomeric composition before and after the incubation/oligomerization step. Such differences in sample composition were also independently confirmed with an in vitro Aβ toxicity study on primary rat cortical neurons. An additional validation was accomplished through removal of oligomers from the sample using molecular weight cutoff filters; the resulting MS data correctly reflected the removal at the expected cutoff points. The results collectively validated the ability of MALDI MS to assess the monomeric/multimeric composition of Aβ samples. Graphical Abstract ᅟ.

Inhibition of Protein Aggregation by Several Antioxidants

Amyloid fibril formation is a shared property of all proteins; therefore, model proteins can be used to study this process. We measured protein aggregation of the model amyloid-forming protein stefin B in the presence and absence of several antioxidants. Amyloid fibril formation by stefin B was routinely induced at pH 5 and 10% TFE, at room temperature. The effects of antioxidants NAC, vitamin C, vitamin E, and the three polyphenols resveratrol, quercetin, and curcumin on the kinetics of fibril formation were followed using ThT fluorescence. Concomitantly, the morphology and amount of the aggregates and fibrils were checked by transmission electron microscopy (TEM). The concentration of the antioxidants was varied, and it was observed that different modes of action apply at low or high concentrations relative to the binding constant. In order to obtain more insight into the possible mode of binding, docking of NAC, vitamin C, and all three polyphenols was done to the monomeric form of stefin B.

Cu(II) binding to various forms of amyloid-β peptides. Are they friends or foes?

In the present micro-review, we describe the Cu(II) binding to several forms of amyloid-β peptides, the peptides involved in Alzheimer's disease. It has indeed been shown that in addition to the "full-length" peptide originating from the precursor protein after cleavage at position 1, several other shorter peptides do exist in large proportion and may be involved in the disease as well. Cu(II) binding to amyloid-β peptides is one of the key interactions that impact both the aggregating properties of the amyloid peptides and the Reactive Oxygen Species (ROS) production, two events linked to the etiology of the disease. Binding sites and affinity are described in correlation with Cu(II) induced ROS formation and Cu(II) altered aggregation, for amyloid peptides starting at position 1, 3, 4, 11 and for the corresponding pyroglutamate forms when they could be obtained (i.e. for peptides cleaved at positions 3 and 11). It appears that the current paradigm which points out a toxic role of the Cu(II) - amyloid-β interaction might well be shifted towards a possible protective role when the peptides considered are the N-terminally truncated ones.

Phytol-loaded PLGA nanoparticle as a modulator of Alzheimer's toxic Aβ peptide aggregation and fibrillation associated with impaired neuronal cell function

Alzheimer's disease (AD) is an unfavourable neurological condition of the brain leading to the loss of behavioural and cognitive skills of the aging population. At present, drugs representing cholinesterase inhibitors provide lateral side effects to AD patients. Hence, there is a need for improved fabrication of drugs without side effects, for which nanoencapsulated bioactive compounds that can cross the blood-brain barrier offer new hope as novel alternative treatment strategy for AD. This study involved synthesis of phytol loaded poly(lactic-co-glycolic acid) (PLGA) nanoparticles by solvent evaporation method. Physico-chemical characterization of phytol-PLGA NPs through the field emission scanning electron microscope, dynamic laser scattering (DLS) measurement revealed that the particles were nanosize range with smooth surface and spherical morphology. Furthermore, the biocompatibility of drug/polymer ratio was investigated by power X-ray diffraction (PXRD) and Fourier-transform infrared spectroscopic (FT-IR) analysis. The in vitro drug release study showed that the phytol was released in a sustained manner. Moreover, phytol-PLGA NPs were able to disrupt amyloid aggregates, exhibit anti-cholinesterase and anti-oxidative property and are non-cytotoxic in Neuro2a cells.

Crystal Structure of the Complex of Human FasL and Its Decoy Receptor DcR3

The apoptotic effect of FasL:Fas signaling is disrupted by DcR3, a unique secreted member of the tumor necrosis factor receptor superfamily, which also binds and neutralizes TL1A and LIGHT. DcR3 is highly elevated in patients with various tumors and contributes to mechanisms by which tumor cells to evade host immune surveillance. Here we report the crystal structure of FasL in complex with DcR3. Comparison of FasL:DcR3 structure with our earlier TL1A:DcR3 and LIGHT:DcR3 structures supports a paradigm involving the recognition of invariant main-chain and conserved side-chain functionalities, which is responsible for the recognition of multiple TNF ligands exhibited by DcR3. The FasL:DcR3 structure also provides insight into the FasL:Fas recognition surface. We demonstrate that the ability of recombinant FasL to induce Jurkat cell apoptosis is significantly enhanced by native glycosylation or by structure-inspired mutations, both of which result in reduced tendency to aggregate. All of these activities are efficiently inhibited by recombinant DcR3.

Chronic stress exposure following photothrombotic stroke is associated with increased levels of Amyloid beta accumulation and altered oligomerisation at sites of thalamic secondary neurodegeneration in mice

Exposure to severe stress following stroke is recognised to complicate the recovery process. We have identified that stress can exacerbate the severity of post-stroke secondary neurodegeneration in the thalamus. In this study, we investigated whether exposure to stress could influence the accumulation of the neurotoxic protein Amyloid-β. Using an experimental model of focal cortical ischemia in adult mice combined with exposure to chronic restraint stress, we examined changes within the contra- and ipsilateral thalamus at six weeks post-stroke using Western blotting and immunohistochemical approaches. Western blotting analysis indicated that stroke was associated with a significant enhancement of the 25 and 50 kDa oligomers within the ipsilateral hemisphere and the 20 kDa oligomer within the contralateral hemisphere. Stroked animals exposed to stress exhibited an additional increase in multiple forms of Amyloid-beta oligomers. Immunohistochemistry analysis confirmed that stroke was associated with a significant accumulation of Amyloid-beta within the thalami of both hemispheres, an effect that was exacerbated in stroke animals exposed to stress. Given that Amyloid-beta oligomers, most notably the 30-40 and 50 kDa oligomers, are recognised to correlate with accelerated cognitive decline, our results suggest that monitoring stress levels in patients recovering from stroke may merit consideration in the future.