The flavonoid derivative 2-(4' Benzyloxyphenyl)-3-hydroxy-chromen-4-one protects against Aβ42-induced neurodegeneration in transgenic Drosophila: insights from in silico and in vivo studies

Recent Advances in Targeting Transition Metals (Copper, Iron, and Zinc) in Alzheimer's Disease

Changes in the transition metal homeostasis in the brain are closely linked with Alzheimer's disease (AD), including intraneuronal iron accumulation and extracellular copper and zinc pooling in the amyloid plague. The brain copper, zinc, and iron surplus are commonly acknowledged characteristics of AD, despite disagreements among some. This has led to the theory that oxidative stress resulting from abnormal homeostasis of these transition metals may be a causative explanation behind AD. In the nervous system, the interaction of metals with proteins appears to be an essential variable in the development or suppression of neurodegeneration. Chelation treatment may be an option for treating neurodegeneration induced by transition metal ion dyshomeostasis. Some clinicians even recommend using chelating agents as an adjunct therapy for AD. The current review also looks at the therapeutic strategies that have been attempted, primarily with metal-chelating drugs. Metal buildup in the nervous system, as reported in the AD, could be the result of compensatory mechanisms designed to improve metal availability for physiological functions.

Exploration of a library of piperonylic acid-derived hydrazones possessing variable aryl functionalities as potent dual cholinesterase and monoamine oxidase inhibitors

A library of piperonylic acid-derived hydrazones possessing variable aryl moiety was synthesized and investigated for their multifunctional properties against cholinesterases (ChEs) and monoamine oxidases (MAOs). The in vitro enzymatic assay results revealed that the tested hydrazones have exhibited excellent cholinesterase inhibition profile. Compound 4i, (E)-N'-(2,3-dichlorobenzylidene)benzo[d][1,3]dioxole-5-carbohydrazide showed promising dual inhibitory profile against AChE (0.048 ± 0.007 μM), BChE (0.89 ± 0.018 μM), and MAO-B (0.95 ± 0.12 μM) enzymes. SAR exploration revealed that the truncation of the linker connecting both the aryl binding sites of the semicarbazone scaffold, by one atom, has relatively suppressed the AChE inhibitory potential. Kinetic studies disclosed that the compound 4i reversibly inhibited AChE enzyme in a competitive manner (Ki = 8.0 ± 0.076 nM), while it displayed a non-competitive and reversible inhibition profile against MAO-B (Ki = 9.6 ± 0.021 µM). Moreover, molecular docking studies of synthesized compounds against ChEs and MAOs provided the crucial molecular features that enable their close association and interaction with the target enzymes. All atomistic simulation studies confirmed the stable association of compound 4i within the active sites of AChE and MAO-B. In addition, theoretical ADMET prediction studies demonstrated the acceptable pharmacokinetic profile of the dual inhibitors. In summary, the attempted lead simplification study afforded a potent dual ChE-MAO-B inhibitor compound that merits further investigation.

Protective Effects of Flavonoids against Alzheimer's Disease: Pathological Hypothesis, Potential Targets, and Structure-Activity Relationship

Alzheimer’s disease (AD) is a neurodegenerative disease with high morbidity and mortality, for which there is no available cure. Currently, it is generally believed that AD is a disease caused by multiple factors, such as amyloid-beta accumulation, tau protein hyperphosphorylation, oxidative stress, and inflammation. Multitarget prevention and treatment strategies for AD are recommended. Interestingly, naturally occurring dietary flavonoids, a class of polyphenols, have been reported to have multiple biological activities and anti-AD effects in several AD models owing to their antioxidative, anti-inflammatory, and anti-amyloidogenic properties. In this review, we summarize and discuss the existing multiple pathogenic factors of AD. Moreover, we further elaborate on the biological activities of natural flavonoids and their potential mode of action and targets in managing AD by presenting a wide range of experimental evidence. The gathered data indicate that flavonoids can be regarded as prophylactics to slow the advancement of AD or avert its onset. Different flavonoids have different activities and varying levels of activity. Further, this review summarizes the structure–activity relationship of flavonoids based on the existing literature and can provide guidance on the design and selection of flavonoids as anti-AD drugs.

Flavonoids as Promising Neuroprotectants and Their Therapeutic Potential against Alzheimer’s Disease

Alzheimer's disease (AD) is one of the serious and progressive neurodegenerative disorders in the elderly worldwide. Various genetic, environmental, and lifestyle factors are associated with its pathogenesis that affect neuronal cells to degenerate over the period of time. AD is characterized by cognitive dysfunctions, behavioural disability, and psychological impairments due to the accumulation of amyloid beta (Aβ) peptides and neurofibrillary tangles (NFT). Several research reports have shown that flavonoids are the polyphenolic compounds that significantly improve cognitive functions and inhibit or delay the amyloid beta aggregation or NFT formation in AD. Current research has uncovered that dietary use of flavonoid-rich food sources essentially increases intellectual abilities and postpones or hinders the senescence cycle and related neurodegenerative problems including AD. During AD pathogenesis, multiple signalling pathways are involved and to target a single pathway may relieve the symptoms but not provides the permanent cure. Flavonoids communicate with different signalling pathways and adjust their activities, accordingly prompting valuable neuroprotective impacts. Flavonoids likewise hamper the movement of obsessive indications of neurodegenerative disorders by hindering neuronal apoptosis incited by neurotoxic substances. In this short review, we briefly discussed about the classification of flavonoids and their neuroprotective properties that could be used as a potential source for the treatment of AD. In this review, we also highlight the structural features of flavonoids, their beneficial roles in human health, and significance in plants as well as their microbial production.

Mitochondria-Related Apoptosis Regulation by Minocycline: A Study on a Transgenic Drosophila Model of Alzheimer's Disease

Alzheimer's disease (AD) is a very complicated and multifactorial neurological disorder having limited therapeutic interventions illustrated by the impairment in memory and cognitive function. Several lines of confirmation are stoutly connected with mitochondrial function perturbation as a significant causative factor in AD, while the molecular mechanisms involved in AD pathogenesis are still poorly understood. Minocycline, a well-known antibiotic, has confirmed efficacy against mitochondrial defects and oxidative stress as a neuroprotective effect. In view of this property, we examined the remedial effect of minocycline on AD. To attain insight into the molecular machinery responsible for AD pathogenesis, we preferred the UAS/GAL4 scheme for the development of AD in flies that overexpress the Aβ42 protein in the brain of Drosophila. The warning signs like the declined lifespan, locomotion deficit and memory loss, impaired mitochondrial membrane potential, and increased caspase 3 expression with mitogen-associated protein kinases linked with AD pathogenesis were examined in the existence of minocycline. Minocycline halted the Aβ42-induced symptoms including behavioral changes and altered the mitochondrial membrane potential along with apoptotic factors' protein expression (JNK/p-JNK and caspase 3). Thus, the current study could be functional to find out the role of minocycline in human Aβ42-overexpressed transgenic AD flies.

Saponins and flavonoids from Bacopa floribunda plant extract exhibit antioxidant and anti-inflammatory effects on amyloid beta 1-42-induced Alzheimer's disease in BALB/c mice

ETHNOPHARMACOLOGICAL RELEVANCE

Bacopa floribunda (BF), a locally available plant has been employed traditionally as memory enhancer in Southwestern, Nigeria. It has been utilized in traditional and Ayurvedic medicine as brain tonic for enhancing memory, anti-aging and forestalling series of psychological disorders. However, there is a dearth of scientific information on the mechanism(s) of action of important phytochemicals from BF extract on dementia.

AIM OF THE STUDY

Alzheimer's disease, the commonest form of dementia has been postulated to triple by 2050 as a result of increase in life expectancy. This study therefore assessed and compared the possible mechanism(s) of action of flavonoids and saponins from BF on Amyloid beta (Aβ1-42)-induced dementia in male BALB/c mice.

MATERIALS AND METHODS

Eighty (80) healthy BALB/c mice divided into 10 groups (n = 8) were given a single bilateral ICV injection of Aβ1-42 or normal saline. Graded doses of Saponins and flavonoids (50, 100 and 200 mg/kg) were used as treatment for 21 days. Hippocampal homogenates were assayed for the levels of antioxidants, oxidative stress and neuroinflammatory markers. In vitro antioxidant activity of flavonoids and saponins were equally assessed using standard procedures. The extent of microglial activation was quantified through immunohistochemistry procedure.

RESULTS

Aβ1-42 successfully caused a spike in hippocampal levels of MDA, IL1β, TNF-α including MPO levels and invariably decreased antioxidant activities. Likewise an increase in reactive microglia (microgliosis) was observed. However, crude saponins and flavonoids from BF were able to suppress microgliosis, oxidative stress and neuroinflammation induced by Aβ1- 42 and were observed to be more effective at higher doses of saponins (100 mg/kg and 200 mg/kg) and flavonoid (100 mg/kg).

CONCLUSIONS

Phytochemicals from BF efficiently exhibited dose dependent alleviation of some symptoms associated with Alzheimer's disease.

Animal Models of Neurodegenerative Disease: Recent Advances in Fly Highlight Innovative Approaches to Drug Discovery

Neurodegenerative diseases represent a formidable challenge to global health. As advances in other areas of medicine grant healthy living into later decades of life, aging diseases such as Alzheimer's disease (AD) and other neurodegenerative disorders can diminish the quality of these additional years, owed largely to the lack of efficacious treatments and the absence of durable cures. Alzheimer's disease prevalence is predicted to more than double in the next 30 years, affecting nearly 15 million Americans, with AD-associated costs exceeding $1 billion by 2050. Delaying onset of AD and other neurodegenerative diseases is critical to improving the quality of life for patients and reducing the burden of disease on caregivers and healthcare systems. Significant progress has been made to model disease pathogenesis and identify points of therapeutic intervention. While some researchers have contributed to our understanding of the proteins and pathways that drive biological dysfunction in disease using in vitro and in vivo models, others have provided mathematical, biophysical, and computational technologies to identify potential therapeutic compounds using in silico modeling. The most exciting phase of the drug discovery process is now: by applying a target-directed approach that leverages the strengths of multiple techniques and validates lead hits using Drosophila as an animal model of disease, we are on the fast-track to identifying novel therapeutics to restore health to those impacted by neurodegenerative disease.

Copper-Mediated β-Amyloid Toxicity and its Chelation Therapy in Alzheimer's Disease

The link between bio-metals, Alzheimer's disease (AD), and its associated protein, amyloid-β (Aβ) is very complex and one of the most studied aspects currently. Alzheimer's disease, a progressive neurodegenerative disease, is proposed to occurs due to the misfolding and aggregation of Aβ. Dyshomeostasis of metal ions and their interaction with Aβ has largely been implicated in AD. Copper plays a crucial role in amyloid-β toxicity and AD development potentially occurs through direct interaction with the copper-binding motif of APP and different amino acid residues of Aβ. Previous reports suggest that high levels of copper accumulation in the AD brain result in modulation of toxic Aβ peptide levels, implicating the role of copper in the pathophysiology of AD. In this review, we explore the possible mode of copper ion interaction with Aβ which accelerates the kinetics of fibril formation and promote amyloid-β mediated cell toxicity in Alzheimer's disease and the potential use of various copper chelators in the prevention of copper-mediated Aβ toxicity.

Aβ42 Expressing Drosophila melanogaster Model for Alzheimer's Disease: Quantitative Proteomics Identifies Altered Protein Dynamics of Relevance to Neurodegeneration

Production and deposition of β-amyloid peptides (Aβ) are among the major hallmarks of the pathogenesis of Alzheimer's disease (AD). Mapping the altered protein dynamics associated with Aβ accumulation and neuronal damage may open up new avenues to innovation for drug target discovery in AD. Using quantitative proteomics, we report new findings from the amyloid beta-peptide with 42 amino acids (Aβ42) expressing Drosophila melanogaster model for AD compared to that of the wild-type flies. We identified 302,241 peptide-spectrum matches with 25,641 nonredundant peptides corresponding to 7959 D. melanogaster proteins. Furthermore, we unraveled 538 significantly altered proteins in Aβ42 expressing flies. These differentially expressed proteins were enriched for biological processes associated with neuronal damage leading to AD progression. We also identified 463 unique post-translational modification events mapping to 202 proteins from the same dataset. Among these, 303 modified peptides corresponding to 246 proteins were also altered in the AD model. These modified proteins are known to be involved in the disruption of molecular functions maintaining neuronal plasticity. This study provides new molecular leads on altered protein dynamics relevant to neurodegeneration, neuroplasticity, and AD progression induced by Aβ42 toxicity. These proteins may prove useful to discover new drugs in an AD model of D. melanogaster and evaluate their efficacy and mode of molecular action in the future.

Neuroprotective potential of flavonoid rich Ascophyllum nodosum (FRAN) fraction from the brown seaweed on an Aβ42 induced Alzheimer's model of Drosophila

BACKGROUND

In Alzheimer Disease (AD) pathogenesis, aggregation of Aβ42 fibrils strongly correlates with memory dysfunction and neurotoxicity. Till date, no promising cures for AD. Report shows that flavonoids contributed anti-oxidant, anti-cancer and neuroprotection activity by regulating the mitochondrial machinery. Here, we first report the identification of flavonoids from Ascophyllum nodosum as having the ability to dissolve Aβ42 fibrils in an AD model of Drosophila. FRAN could be superior anti-AD agents for neuroprotection, their underlying mechanism and how they collectively halted amyloidogenesis is currently being investigated.

PURPOSE

This study aimed to investigate the neuroprotective role of FRAN in the Aβ42 expressing AD model of Drosophila.

METHODS

Drosophila stocks: OregonR+, ey-GAL4/CyO, elavc155-GAL4, UAS-mitoGFP, UAS-mcherry.mito.OMM, UAS-Aβ42/CyO were used, cultured at 28±1 °C in a BOD incubator. Ascophyllum extract rich in flavonoids as revealed by LC-MS study and employed against the AD flies. The validation of Aβ42 expression was done by immunostaining and q-RT PCR. The eye roughness of AD flies was scored in a dose-dependent manner. Further, In vivo and in silico studies of FRAN extract was executed against Aβ42 induced neurotoxicity.

RESULTS

In order to determine the most effective lethal dose of FRAN extract concentration 1, 2, 5, 10 mg/ml were screened using OregonR+flies. Extract 1 and 2 mg/ml did not show any lethality. Hence, extract 2 mg/ml was employed on AD flies and a ≥ 50% rescue in the eye phenotype was observed using SEM images. This dose had a strong effect on cell apoptosis, viability, longevity, mitochondrial dysfunction and oxidative stress by regulating mitochondrial dynamic markers in comparable to control. Extract also scavenging free radicals in order to maintain in situ cellular ROS and prevent Aβ42-induced neurotoxicity in vivo and in silico. Hence, we suggest its great potential as a future therapeutic agent for AD treatment.

CONCLUSION

In conclusion, FRAN extract rich in flavonoids as having largest neuroprotective activity against Aβ42 aggregation in eye tissue of Drosophila. Extract shows strong effect against Aβ42-induced neurotoxicity by altering the various cellular and molecular events. So, it could be considered as strong anti-AD agents for neuroprotection.

Characterisation of twelve newly synthesised N-(substituted phenyl)-2-chloroacetamides with QSAR analysis and antimicrobial activity tests

In this study we screened twelve newly synthesised N-(substituted phenyl)-2-chloroacetamides for antimicrobial potential relying on quantitative structure-activity relationship (QSAR) analysis based on the available cheminformatics prediction models (Molinspiration, SwissADME, PreADMET, and PkcSM) and verified it through standard antimicrobial testing against Escherichia coli, Staphylococcus aureus, methicillin-resistant S. aureus (MRSA), and Candida albicans. Our compounds met all the screening criteria of Lipinski’s rule of five (Ro5) as well as Veber’s and Egan’s methods for predicting biological activity. In antimicrobial activity tests, all chloroacetamides were effective against Gram-positive S. aureus and MRSA, less effective against the Gram-negative E. coli, and moderately effective against the yeast C. albicans. Our study confirmed that the biological activity of chloroacetamides varied with the position of substituents bound to the phenyl ring, which explains why some molecules were more effective against Gram-negative than Gram-positive bacteria or C. albicans. Bearing the halogenated p-substituted phenyl ring, N-(4-chlorophenyl), N-(4-fluorophenyl), and N-(3-bromophenyl) chloroacetamides were among the most active thanks to high lipophilicity, which allows them to pass rapidly through the phospholipid bilayer of the cell membrane. They are the most promising compounds for further investigation, particularly against Gram-positive bacteria and pathogenic yeasts.

Effect of melatonin on Aβ42 induced changes in the mitochondrial function related to Alzheimer's disease in Drosophila melanogaster

Alzheimers's disease is one of the alarming neurodegenerative disease and it is of global concern.The hallmarks of the disease are the amyloid beta (Aβ) aggregation and presence of neurofibrillary tangles (NFTs). The interaction of Aβ with macromolecular targets affects the normal cellular functions. The amyloid peptide interaction with cellular surfaces may trigger the intracellular cascades of signalling. Interaction of Aβ with mitochondria leads to the generation of free radicals. Many studies have suggested the involvement of mitochondrial dysfunction in Alzheimer's disease. Melatonin prevents mitochondria stress and by means of activating the antioxidant systems it protects the death of neurons. Although the study have been already conducted on Aβ42 infused or injury induced animal models but till date there is no reports of such studies on transgenic model of Drosophila melanogaster. In the present study, we have taken UAS/Gal4 system for the development of transgenic flies that overexpress Aβ42 in the brain of Drosophila. With the help of these transgenic flies we have analyse different experiments like behavioural parameters, oxidative stress parameters and protein expression through western blotting in the presence of melatonin. We have found that melatonin significantly ameliorated the toxicity caused by the Aβ42 overexpression. Thus the present study could be beneficial to find out the role of melatonin in transgenic flies overexpressing human Aβ42.

Neuroprotective and Antioxidant Effect of Ginkgo biloba Extract Against AD and Other Neurological Disorders

Alzheimer's disease (AD) is the most common progressive human neurodegenerative disorder affecting elderly population worldwide. Hence, prevention of AD has been a priority of AD research worldwide. Based on understanding of disease mechanism, different therapeutic strategies involving synthetic and herbal approaches are being used against AD. Among the herbal extract, Ginkgo biloba extract (GBE) is one of the most investigated herbal remedy for cognitive disorders and Alzheimer's disease (AD). Standardized extract of Ginkgo biloba is a popular dietary supplement taken by the elderly population to improve memory and age-related loss of cognitive function. Nevertheless, its efficacy in the prevention and treatment of dementia remains controversial. Specifically, the added effects of GBE in subjects already receiving "conventional" anti-dementia treatments have been to date very scarcely investigated. This review summarizes recent advancements in our understanding of the potential use of Ginkgo biloba extract in the prevention of AD including its antioxidant property. A better understanding of the mechanisms of action of GBE against AD will be important for designing therapeutic strategies, for basic understanding of the underlying neurodegenerative processes, and for a better understanding of the effectiveness and complexity of this herbal medicine.

3'-Hydroxy-3,4'-dimethoxyflavone blocks tubulin polymerization and is a potent apoptotic inducer in human SK-MEL-1 melanoma cells

Flavonoids are naturally occurring polyphenolic compounds and are among the most promising anticancer agents. A series of flavonols and their 3-methyl ether derivatives were synthesized and assessed for cytotoxicity. It was found that 3'-hydroxy-3,4'-dimethoxyflavone (flavonoid 7a) displayed strong cytotoxicity against human SK-MEL-1 melanoma cells and blocked tubulin polymerization, but had no significant cytotoxic effects against quiescent or proliferating human peripheral blood mononuclear cells. Our analyses showed that flavonoid 7a induces G₂-M cell cycle arrest and apoptosis in melanoma cells which is associated with cytochrome c release and activation of both extrinsic and intrinsic apoptotic pathways of cell death.

Investigation of naphthofuran moiety as potential dual inhibitor against BACE-1 and GSK-3β: molecular dynamics simulations, binding energy, and network analysis to identify first-in-class dual inhibitors against Alzheimer's disease

BACE-1 and GSK-3β are potential therapeutic drug targets for Alzheimer's disease. Recently, both the targets received attention for designing dual inhibitors for Alzheimer's disease. Until now, only two-scaffold triazinone and curcumin have been reported as BACE-1 and GSK-3β dual inhibitors. Docking, molecular dynamics, clustering, binding energy, and network analysis of triazinone derivatives with BACE-1 and GSK-3β was performed to get molecular insight into the first reported dual inhibitor. Further, we designed and evaluated a naphthofuran series for its ability to inhibit BACE-1 and GSK-3β with the computational approaches. Docking study of naphthofuran series showed a good binding affinity towards both the targets. Molecular dynamics, binding energy, and network analysis were performed to compare their binding with the targets and amino acids responsible for binding. Naphthofuran series derivatives showed good interaction within the active site residues of both of the targets. Hydrogen bond occupancy and binding energy suggested strong binding with the targets. Dual-inhibitor binding was mostly governed by the hydrophobic interactions for both of the targets. Per residue energy decomposition and network analysis identified the key residues involved in the binding and inhibiting BACE-1 and GSK-3β. The results indicated that naphthofuran series derivative 11 may be a promising first-in-class dual inhibitor against BACE-1 and GSK-3β. This naphthofuran series may be further explored to design better dual inhibitors. Graphical abstract Naphthofuran derivative as a dual inhibitor for BACE-1 and GSK-3β.

Novel benzopyran derivatives and their therapeutic applications: a patent review (2009-2016)

INTRODUCTION

The benzopyran derivatives present a wide variety of biological activity and behaviour. At the same time the benzopyran derivatives support their use as therapeutic agents for multiple diseases. Their structural characteristics correlated to physicochemical properties seem to define the extent of the biological activity. Areas covered: This review summarizes new patents published on new benzopyran derivatives from 2009 to 2016. Expert opinion: Many benzopyran derivatives have vivo/vitro biological responses. Their clinical evaluation will be critical to assess therapeutic utility. The compounds containing benzopyran moiety is well defined as lead compounds for design of new more promising molecules.

NSAIDs as potential treatment option for preventing amyloid β toxicity in Alzheimer's disease: an investigation by docking, molecular dynamics, and DFT studies

Aggregation of amyloid beta (Aβ) protein considered as one of contributors in development of Alzheimer's disease (AD). Several investigations have identified the importance of non-steroidal anti-inflammatory drugs (NSAIDs) as Aβ aggregation inhibitors. Here, we have examined the binding interactions of 24 NSAIDs belonging to eight different classes, with Aβ fibrils by exploiting docking and molecular dynamics studies. Minimum energy conformation of the docked NSAIDs were further optimized by density functional theory (DFT) employing Becke's three-parameter hybrid model, Lee-Yang-Parr (B3LYP) correlation functional method. DFT-based global reactivity descriptors, such as electron affinity, hardness, softness, chemical potential, electronegativity, and electrophilicity index were calculated to inspect the expediency of these descriptors for understanding the reactive nature and sites of the molecules. Few selected NSAID-Aβ fibrils complexes were subjected to molecular dynamics simulation to illustrate the stability of these complexes and the most prominent interactions during the simulated trajectory. All of the NSAIDs exhibited potential activity against Aβ fibrils in terms of predicted binding affinity. Sulindac was found to be the most active compound underscoring the contribution of indene methylene substitution, whereas acetaminophen was observed as least active NSAID. General structural requirements for interaction of NSAIDs with Aβ fibril include: aryl/heteroaryl aromatic moiety connected through a linker of 1-2 atoms to a distal aromatic group. Considering these structural requirements and electronic features, new potent agents can be designed and developed as potential Aβ fibril inhibitors for the treatment of AD.

Knockdown of APPL mimics transgenic Aβ induced neurodegenerative phenotypes in Drosophila

A variety of Drosophila mutant lines have been established as potential disease-models to study various disease mechanisms including human neurodegenerative diseases like Alzheimer's disease (AD), Huntington's disease (HD) and Parkinson's disease (PD). The evolutionary conservation of APP (Amyloid Precursor Protein) and APPL (Amyloid Precursor Protein-Like) and the comparable detrimental effects caused by their metabolic products strongly implies the conservation of their normal physiological functions. In view of this milieu, a comparative analysis on the pattern of neurodegenerative phenotypes between Drosophila APPL-RNAi line and transgenic Drosophila line expressing eye tissue specific human Aβ (Amyloid beta) was undertaken. Our results clearly show that Drosophila APPL-RNAi largely mimics transgenic Aβ in various phenotypes which include eye degeneration, reduced longevity and motor neuron deficit functions, etc. The ultra-structural morphological pattern of eye degeneration was confirmed by scanning electron microscopy. Further, a comparative study on longevity and motor behaviour between Aβ expressing and APPL knockdown lines revealed similar kind of behavioural deficit and longevity phenotypes. Therefore, it is suggested that APPL-knockdown approach can be used as an alternative approach to study neurodegenerative diseases in the fly model. To the best of our knowledge this is the first report showing comparable phenotypes between APPL and Aβ in AD model of Drosophila.

Bioactive polyphenol interactions with β amyloid: a comparison of binding modelling, effects on fibril and aggregate formation and neuroprotective capacity

In this study we compared the effects of a diverse set of natural polyphenolics ligands on in silico interactive modelling, in vitro anti-aggregative properties and neuronal toxicity of β amyloid. The β amyloid-binding characteristics of optimised structural conformations of polyphenols with ascribed neuroprotective actions including punicalagin, myricetin, luteolin and honokiol were determined in silico. Thioflavin T and transmission electron microscopy were used to assess in vitro inhibitory effects of these polyphenols on Aβ1-42 fibril and aggregation formation. Phaeochromocytoma (PC12) cells were exposed to Aβ1-42, alone and in combination with test concentrations of each polyphenol (100 μM) and viability measured using MTT assay. Aβ1-42 evoked a concentration-dependent loss of cell viability in PC12 cells, in which all four polyphenols demonstrated significant inhibition of neurotoxicity. While all compounds variably altered the morphology of Aβ aggregation, the flavonoids luteolin and myricetin and the lignan honokiol all bound in a similar hydrophobic region of the amyloid pentamer and exerted the most pronounced inhibition of Aβ1-42 aggregation. Each of the polyphenols demonstrated neuroprotective effects in PC12 cells exposed to Aβ1-42, including punicalagin. These findings highlight some structure-activity insights that can be gleaned into the anti-aggregatory properties of bioactive polyphenols based on modelling of their binding to β-amyloid, but also serve to highlight the more general cellular neuroprotective nature of such compounds.

Alzheimer's disease: the silver tsunami of the 21(st) century

Alzheimer's disease (AD), a fatal progressive neurodegenerative disorder, has no cure to date. One of the causes of AD is the accumulation of amyloid-beta 42 (Aβ42) plaques, which result in the onset of neurodegeneration. It is not known how these plaques trigger the onset of neurodegeneration. There are several animal models developed to (i) study etiology of disease, (ii) look for genetic modifiers, and (iii) identify chemical inhibitors that can block neurodegeneration and help to find cure for this disease. An insect model of Drosophila melanogaster has also provided new insights into the disease. Here we will discuss the utility of the Drosophila eye model to study Alzheimer's disease.

Overview of Alzheimer's Disease and Some Therapeutic Approaches Targeting Aβ by Using Several Synthetic and Herbal Compounds

Alzheimer's disease (AD) is a complex age-related neurodegenerative disease. In this review, we carefully detail amyloid-β metabolism and its role in AD. We also consider the various genetic animal models used to evaluate therapeutics. Finally, we consider the role of synthetic and plant-based compounds in therapeutics.

Molecular insight into amyloid oligomer destabilizing mechanism of flavonoid derivative 2-(4' benzyloxyphenyl)-3-hydroxy-chromen-4-one through docking and molecular dynamics simulations

Aggregation of amyloid peptide (Aβ) has been shown to be directly related to progression of Alzheimer's disease (AD). Aβ is neurotoxic and its deposition and aggregation ultimately lead to cell death. In our previous work, we reported flavonoid derivative (compound 1) showing promising result in transgenic AD model of Drosophila. Compound 1 showed prevention of Aβ-induced neurotoxicity and neuroprotective efficacy in Drosophila system. However, mechanism of action of compound 1 and its effect on the amyloid is not known. We therefore performed molecular docking and atomistic, explicit-solvent molecular dynamics simulations to investigate the process of Aβ interaction, inhibition, and destabilizing mechanism. Results showed different preferred binding sites of compound 1 and good affinity toward the target. Through the course of 35 ns molecular dynamics simulation, conformations_5 of compound 1 intercalates into the hydrophobic core near the salt bridge and showed major structural changes as compared to other conformations. Compound 1 showed interference with the salt bridge and thus reducing the inter strand hydrogen bound network. This minimizes the side chain interaction between the chains A-B leading to disorder in oligomer. Contact map analysis of amino acid residues between chains A and B also showed lesser interaction with adjacent amino acids in the presence of compound 1 (conformations_5). The study provides an insight into how compound 1 interferes and disorders the Aβ peptide. These findings will further help to design better inhibitors for aggregation of the amyloid oligomer.

Virtual and In Vitro Screens Reveal a Potential Pharmacophore that Avoids the Fibrillization of Aβ1-42

Among the multiple factors that induce Alzheimer’s disease, aggregation of the amyloid β peptide (Aβ) is considered the most important due to the ability of the 42-amino acid Aβ peptides (Aβ_1–42) to form oligomers and fibrils, which constitute Aβ pathological aggregates. For this reason, the development of inhibitors of Aβ_1–42 pathological aggregation represents a field of research interest. Several Aβ_1–42 fibrillization inhibitors possess tertiary amine and aromatic moieties. In the present study, we selected 26 compounds containing tertiary amine and aromatic moieties with or without substituents and performed theoretical studies that allowed us to select four compounds according to their free energy values for Aβ_1–42 in α-helix (Aβ-α), random coil (Aβ-RC) and β-sheet (Aβ-β) conformations. Docking studies revealed that compound 5 had a higher affinity for Aβ-α and Aβ-RC than the other compounds. In vitro, this compound was able to abolish Thioflavin T fluorescence and favored an RC conformation of Aβ_1–42 in circular dichroism studies, resulting in the formation of amorphous aggregates as shown by atomic force microscopy. The results obtained from quantum studies allowed us to identify a possible pharmacophore that can be used to design Aβ_1–42 aggregation inhibitors. In conclusion, compounds with higher affinity for Aβ-α and Aβ-RC prevented the formation of oligomeric species.

Engineering of a peptide probe for β-amyloid aggregates

A non-self-aggregating peptide ligand for β-amyloid aggregates created by simple point mutation of an β-amyloid-derived segment.