curcumin and Protein-Aggregation--Pathological

Alzheimer's disease (AD) is the most common form of dementia characterized by presence of extracellular amyloid plaques and intracellular neurofibrillary tangles composed of tau protein. Currently there are close to 50 million people living with dementia and this figure is expected to increase to 75 million by 2030 putting a huge burden on the economy due to the health care cost. Considering the effects on quality of life of patients and the increasing burden on the economy, there is an enormous need of new disease modifying therapies to tackle this disease. The current therapies are dominated by only symptomatic treatments including cholinesterase inhibitors and N-methyl-D-aspartate receptor blockers but no disease modifying treatments exist so far. After several failed attempts to develop drugs against amyloidopathy, tau targeting approaches have been in the main focus of drug development against AD. After an overview of the tauopathy in AD, this review summarizes recent findings on the development of small molecules as therapeutics targeting tau modification, aggregation, and degradation, and tau-oriented multi-target directed ligands. Overall, this work aims to provide a comprehensive and critical overview of small molecules which are being explored as a lead candidate for discovering drugs against tauopathy in AD.

Topics: Alzheimer Disease; Animals; Benzodioxoles; Cholinesterase Inhibitors; Cholinesterases; Curcumin; Humans; Molecular Targeted Therapy; Neurofibrillary Tangles; Neuroprotective Agents; Phosphorylation; Plaque, Amyloid; Protein Aggregation, Pathological; Protein Processing, Post-Translational; Quinazolines; Receptors, N-Methyl-D-Aspartate; tau Proteins; Thiadiazoles

Parkinson's disease (PD) is a movement disorder associated with severe loss of mainly dopaminergic neurons in the substantia nigra. Pathological hallmarks include Lewy bodies, and loss of neuromelanin, due to degeneration of neuromelanin-containing dopaminergic neurons. Despite being described over 200 years ago, the etiology of PD remains unknown. Here, we highlight the roles of reactive oxygen species (ROS), iron, alpha synuclein (α-syn) and neuromelanin in a toxic feedback loop culminating in neuronal death and spread of the disease. Dopaminergic neurons are particularly vulnerable due to decreased antioxidant concentration with aging, constant exposure to ROS and presence of neurotoxic compounds (e.g. ortho-quinones). ROS and iron increase each other's levels, creating a state of oxidative stress. α-Syn aggregation is influenced by ROS and iron but also increases ROS and iron via its induced mitochondrial dysfunction and ferric-reductase activity. Neuromelanin's binding affinity is affected by increased ROS and iron. Furthermore, during neuronal death, neuromelanin is degraded in the extracellular space, releasing its bound toxins. This cycle of events continues to neighboring neurons in the form of a toxic loop, causing PD pathology. The increase in ROS and iron may be an important target for therapies to disrupt this toxic loop, and therefore diets rich in certain 'nutraceuticals' may be beneficial. Turmeric is an attractive candidate, as it is known to have anti-oxidant and iron chelating properties. More studies are needed to test this theory and if validated, this would be a step towards development of lifestyle-based therapeutic modalities to complement existing PD treatments.

Topics: alpha-Synuclein; Animals; Autophagy; Brain Chemistry; Curcuma; Dopamine; Dopaminergic Neurons; Feedback, Physiological; Ferroptosis; Homeostasis; Humans; Iron; Melanins; Mice; Oxidative Stress; Parkinson Disease; Parkinsonian Disorders; Phytotherapy; Protein Aggregation, Pathological; Reactive Oxygen Species; Substantia Nigra

Currently available pharmacological treatment of post-ischemia-reperfusion brain injury has limited effectiveness. This review provides an assessment of the current state of neurodegeneration treatment due to ischemia-reperfusion brain injury and focuses on the role of curcumin in the diet. The purpose of this review was to provide a comprehensive overview of what was published about the benefits of curcumin influence on post-ischemic brain damage. Some data on the clinical benefits of curcumin treatment of post-ischemic brain in terms of clinical symptoms and adverse reactions have been reviewed. The data in this review contributes to a better understanding of the potential benefits of curcumin in the treatment of neurodegenerative changes after ischemia and informs scientists, clinicians, and patients, as well as their families and caregivers about the possibilities of such treatment. Due to the pleotropic properties of curcumin, including anti-amyloid, anti-tau protein hyperphosphorylation, anti-inflammatory, anti-apoptotic, and neuroprotective action, as well as increasing neuronal lifespan and promoting neurogenesis, curcumin is a promising candidate for the treatment of post-ischemic neurodegeneration with misfolded proteins accumulation. In this way, it may gain interest as a potential therapy to prevent the development of neurodegenerative changes after cerebral ischemia. In addition, it is a safe substance and inexpensive, easily accessible, and can effectively penetrate the blood-brain barrier and neuronal membranes. In conclusion, the evidence available in a review of the literature on the therapeutic potential of curcumin provides helpful insight into the potential clinical utility of curcumin in the treatment of neurological neurodegenerative diseases with misfolded proteins. Therefore, curcumin may be a promising supplementary agent against development of neurodegeneration after brain ischemia in the future. Indeed, there is a rational scientific basis for the use of curcumin for the prophylaxis and treatment of post-ischemic neurodegeneration.

Topics: Amyloid; Amyloidogenic Proteins; Animals; Brain Ischemia; Curcumin; Humans; Neurodegenerative Diseases; Neurogenesis; Neurons; Neuroprotective Agents; Phosphorylation; Protein Aggregates; Protein Aggregation, Pathological; tau Proteins

A host of human diseases, including Parkinson's disease and Dementia with Lewy bodies, are suspected to be directly linked to protein aggregation. Amyloid protein aggregates and oligomeric intermediates of α-synuclein are observed in synucleinopathies and considered to be mediators of cellular toxicity. Hence, α-synuclein has seen as one of the leading and most compelling targets and is receiving a great deal of attention from researchers. Nevertheless, there is no neuroprotective approach directed toward Parkinson's disease or other synucleinopathies so far. In this review, we summarize the available data concerning inhibitors of α-synuclein aggregation and their advancing towards clinical use. The compounds are grouped according to their chemical structures, providing respective insights into their mechanism of action, pharmacology, and pharmacokinetics. Overall, shared structure-activity elements are emerging, as well as specific binding modes related to the ability of the modulators to establish hydrophobic and hydrogen bonds interactions with the protein. Some molecules with encouraging in vivo data support the possibility of translation to the clinic.

Topics: alpha-Synuclein; Amyloidogenic Proteins; Drug Discovery; Humans; Protein Aggregation, Pathological; Structure-Activity Relationship

Topics: Amyotrophic Lateral Sclerosis; Animals; Antirheumatic Agents; Clinical Trials as Topic; Curcumin; Drug Evaluation, Preclinical; Humans; Microbiota; Oxidative Stress; Protein Aggregation, Pathological

There is a crucial need to develop new effective drugs for Alzheimer's disease (AD) as the currently available AD treatments provide only momentary and incomplete symptomatic relief. Amongst natural products, curcumin, a major constituent of turmeric, has been intensively investigated for its neuroprotective effect against β-amyloid (Aβ)-induced toxicity in cultured neuronal cells. The ability of curcumin to attach to Aβ peptide and prevent its accumulation is attributed to its three structural characteristics such as the presence of two aromatic end groups and their co-planarity, the length and rigidity of the linker region and the substitution conformation of these aromatics. However, curcumin failed to reach adequate brain levels after oral absorption in AD clinical trials due to its low water solubility and poor oral bioavailability. A number of new curcumin analogs that mimic the active site of the compound along with analogs that mimic the curcumin anti-amyloid effect combined with anticholinesterase effect have been developed to enhance the bioavailability, pharmacokinetics, water solubility, stability at physiological conditions and delivery of curcumin. In this article, we have summarized all reported synthetic analogs of curcumin showing effects on β-amyloid and discussed their potential as therapeutic and diagnostic agents for AD.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Brain; Curcumin; Humans; Neuroprotective Agents; Protein Aggregates; Protein Aggregation, Pathological

The intra- and extracellular accumulation of misfolded and aggregated amyloid proteins is a common feature in several neurodegenerative diseases, which is thought to play a major role in disease severity and progression. The principal machineries maintaining proteostasis are the ubiquitin proteasomal and lysosomal autophagy systems, where heat shock proteins play a crucial role. Many protein aggregates are degraded by the lysosomes, depending on aggregate size, peptide sequence, and degree of misfolding, while others are selectively tagged for removal by heat shock proteins and degraded by either the proteasome or phagosomes. These systems are compromised in different neurodegenerative diseases. Therefore, developing novel targets and classes of therapeutic drugs, which can reduce aggregates and maintain proteostasis in the brains of neurodegenerative models, is vital. Natural products that can modulate heat shock proteins/proteosomal pathway are considered promising for treating neurodegenerative diseases. Here we discuss the current knowledge on the role of HSPs in protein misfolding diseases and knowledge gained from animal models of Alzheimer's disease, tauopathies, and Huntington's diseases. Further, we discuss the emerging treatment regimens for these diseases using natural products, like curcumin, which can augment expression or function of heat shock proteins in the cell.

Topics: Alzheimer Disease; Curcumin; Heat-Shock Proteins; Humans; Huntington Disease; Molecular Chaperones; Neurodegenerative Diseases; Protein Aggregation, Pathological; Protein Folding; Proteostasis Deficiencies; Ubiquitin

In this review, we elucidate the mechanisms of Aβ oligomer toxicity which may contribute to Alzheimer's disease (AD). In particular, we discuss on the interaction of Aβ oligomers with the membrane through the process of adsorption and insertion. Such interaction gives rises to phase transitions in the sub-structures of the Aβ peptide from α-helical to β-sheet structure. By means of a coarse-grained model, we exhibit the tendency of β-sheet structures to aggregate, thus providing further insights to the process of membrane induced aggregation. We show that the aggregated oligomer causes membrane invagination, which is a precursor to the formation of pore structures and ion channels. Other pathological progressions to AD due to Aβ oligomers are also covered, such as their interaction with the membrane receptors, and their direct versus indirect effects on oxidative stress and intraneuronal accumulation. We further illustrate that the molecule curcumin is a potential Aβ toxicity inhibitor as a β-sheet breaker by having a high propensity to interact with certain Aβ residues without binding to them. The comprehensive understanding gained from these current researches on the various toxicity mechanisms show promises in the provision of better therapeutics and treatment strategies in the near future.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Anti-Inflammatory Agents, Non-Steroidal; Cell Membrane; Curcumin; Humans; Protein Aggregation, Pathological; Protein Structure, Secondary

A series of benzofuran piperidine derivatives were designed, synthesized and evaluated as multifunctional Aβ antiaggregant to treat Alzheimer's disease (AD). In vitro results revealed that all of them are very good Aβ antiaggregants and some of the compounds are potent acetylcholinesterase (AChE) inhibitors with moderate antioxidant property. Selected compounds were also tested for neuroprotection activity, LDH release, ATP production and inhibitory activity to prevent Aβ peptides binding to the cell membrane. The different modifications introduced in the structure of our lead compound 3 (hAChE IC

Topics: Acetylcholinesterase; Alzheimer Disease; Amyloid beta-Peptides; Benzofurans; Cholinesterase Inhibitors; Dose-Response Relationship, Drug; Humans; Models, Molecular; Molecular Structure; Neuroprotective Agents; Piperidines; Protein Aggregates; Protein Aggregation, Pathological; Structure-Activity Relationship

A series of phthalide alkyl tertiary amine derivatives were designed, synthesized and evaluated as potential multi-target agents against Alzheimer's disease (AD). The results indicated that almost all the compounds displayed significant AChE inhibitory and selective activities. Besides, most of the derivatives exhibited increased self-induced Aβ

Topics: Acetylcholinesterase; Alzheimer Disease; Amines; Amyloid beta-Peptides; Animals; Butyrylcholinesterase; Cholinesterase Inhibitors; Drug Design; Female; Male; Membranes, Artificial; Mice; Models, Molecular; Molecular Docking Simulation; Molecular Structure; Permeability; Protein Aggregation, Pathological; Random Allocation; Rats

A novel series of triazole tethered coumarin-benzotriazole hybrids based on donepezil skeleton has been designed and synthesized as multifunctional agents for the treatment of Alzheimer's disease (AD). Among the synthesized compounds 13b showed most potent acetylcholinesterase (AChE) inhibition (IC

Topics: Acetylcholinesterase; Alzheimer Disease; Amyloid beta-Peptides; Cell Line, Tumor; Cholinesterase Inhibitors; Coumarins; Dose-Response Relationship, Drug; Humans; Molecular Structure; Peptide Fragments; Protein Aggregates; Protein Aggregation, Pathological; Structure-Activity Relationship; Triazoles

A novel series of deoxyvasicinone-tetrahydro-beta-carboline hybrids were synthesized and evaluated as acetylcholinesterase (AChE) and β-amyloid peptide (Aβ) aggregation inhibitors for the treatment of Alzheimer's disease. The results revealed that the derivatives had multifunctional profiles, including AChE inhibition, Aβ

Topics: Acetylcholinesterase; Alkaloids; Alzheimer Disease; Amyloid beta-Peptides; Carbolines; Cell Line; Cholinesterase Inhibitors; Humans; Molecular Docking Simulation; Peptide Fragments; Protein Aggregates; Protein Aggregation, Pathological

Objectives Alzheimer's disease (AD) is a chronic and progressive neurodegenerative disease in which one of the most prominent pathological features is accumulation of amyloid (Aβ) plaques. This occurs due to the process of aggregation from monomeric to polymeric forms of Aβ peptide and thus represents one of the attractive targets to treat AD. Methods After initial evaluation of a set of molecules containing N-acetylpyrazoline moiety flanked by aromatic rings on both sides as Aβ aggregation inhibitors, the most potent molecules were further investigated for mechanistic insights. These were carried out by employing techniques such as circular dichroism (CD) spectroscopy, transmission electron microscopy (TEM), in vitro PAMPA-BBB (Blood-Brain Barrier) assay and cytotoxicity evaluation. Results Two molecules among the exploratory set displayed Aβ aggregation inhibition comparable to standard curcumin. Among the follow-up molecules, several molecules displayed more inhibition than curcumin. These molecules displayed good inhibitory activity even at lower concentrations. CD and TEM confirmed the mechanism of Aβ aggregation. These molecules were found to alleviate Aβ induced cytotoxicity. BBB penetration studies highlighted the potential of these molecules to reach central nervous system (CNS). Conclusions Thus, several promising Aβ-aggregation inhibitors were obtained as a result of this study.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Cell Survival; Curcumin; Dose-Response Relationship, Drug; Molecular Docking Simulation; Molecular Structure; Protein Aggregates; Protein Aggregation, Pathological; Pyrazoles; Rats

Curcumin and related compounds have been validated to remove even well-developed human β-amyloid plaques from the brain of transgenic mice, in vivo. However, their molecular mechanism of the plaque buster activity is rather unknown. Computational chemistry was employed here to better understand the β-amyloid protein elimination. According to our docking studies, a tautomeric "keto-enol" flip-flop mechanism is proposed that may chop up β-amyloid plaques in Alzheimer's due to removing each hairpin-foldamers one by one from both ends of aggregated fibrils. According to the experimented models, other bi-stable "keto-enol" pharmacophores might be identified to break up amyloid plaques and enhance rapid clearance of toxic aggregates in Alzheimer's disease.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Brain; Curcumin; Dietary Supplements; Humans; In Vitro Techniques; Mice; Mice, Transgenic; Molecular Docking Simulation; Phytotherapy; Plaque, Amyloid; Protein Aggregates; Protein Aggregation, Pathological; Protein Binding

To target the multi-facets of Alzheimer's disease (AD), a series of novel GSK-3β inhibitors containing the 2,3-diaminopyridine moiety were designed and synthesized. The amide derivatives 5a-f showed moderate potency against GSK-3β with weak Cu

Topics: Alzheimer Disease; Amides; Amines; Animals; Antioxidants; Blood-Brain Barrier; Cell Line; Chelating Agents; Drug Design; Glycogen Synthase Kinase 3 beta; Humans; PC12 Cells; Protein Aggregation, Pathological; Protein Kinase Inhibitors; Rats; Structure-Activity Relationship; tau Proteins

The main factors of Alzheimer's disease (AD) are the cerebral accumulation and the formation of extracellular amyloid plaques. The Aβ peptides are highly able to accumulative and produce fibrils that are placed to form these plaques in the AD. The biological action and drug delivery properties of curcumin (Cur) nanoformulation in the Alzheimer's disease therapeutics can be developed by the altering surface of the Poly-lactide-co-glycolide (PLGA) polymer and encapsulation of selenium nanoparticles (Se NPs). The morphological structure, size distributions of nanospheres, chemical interactions between the polymer and nanoformulations of synthesized curcumin and Se NPs loaded PLGA nanospheres have been studied by using the techniques of analytical instruments. The microscopic and nano observation results of synthesized Cur loaded nanospheres are exhibited that the mono-dispersed distributions of particles with spherical shaped structure. The present drug delivery system of Cur loaded Se-PLGA nanospheres could be decreases the amyloid-β load in the brains samples of AD mice, and greatly cured the memory deficiency of the model mice. The specific binding of Cur loaded Se-PLGA nanospheres with Aβ plaques were visualized by fluorescence microscopic technique. Se-PLGA targeting delivery system to amyloid plaques might be providing the enhanced therapeutic efficacy in AD lesions, which was studied by using transgenic mice (5XFAD). In conclusion, Cur loaded Se-PLGA nanoformulation has been demonstrated that valued delivery system for the targeted delivery and effective way to treat AD.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Curcumin; Drug Delivery Systems; Mice; Nanoparticles; Nanospheres; Plaque, Amyloid; Polylactic Acid-Polyglycolic Acid Copolymer; Protein Aggregation, Pathological; Selenium

Curcumin is a natural product with multiple biological activities and numerous potential therapeutic applications. In present study, the influence of curcumin and its degradation products (DPs) on the amyloid aggregation of Tau protein and the related PHF6 peptide were investigated. We provided experimental/theoretical evidence for suppressing effects of the compounds on the amyloid formation using far-UV CD as well as AFM, XRD and docking techniques and showed that the parent curcumin displayed stronger inhibition effect against Tau fibril aggregation. The obtained results suggest that the curcumin/DPs binding sites on the Tau molecule are likely to be the same, and provide a good structural basis to explain the efficient aggregation suppressing behavior of the curcumin, compared to the DPs. So, developing more stable curcumin nanoparticle formulations with improved curcumin bioavailability are of great importance. Curcumin's multi-functionality is also highly significant for the therapeutic application of this natural compound against various human diseases.

Topics: Amyloid; Amyloid beta-Peptides; Amyloidogenic Proteins; Amyloidosis; Binding Sites; Carrier Proteins; Curcumin; Functional Food; Humans; Microscopy, Atomic Force; Oligopeptides; Protein Aggregation, Pathological; tau Proteins; X-Ray Diffraction

A novel series of donepezil based multi-functional agents "(E)-5,6-dimethoxy-2-(4-(4-substituted piperazin-1-yl)benzylidene)-2,3-dihydro-1H-inden-1-ones" have been designed and synthesized as potential anti-Alzheimer's agents. In-vitro studies revealed that these compounds demonstrated moderate to good AChE and Aβ aggregation inhibitory activity. These derivatives are also endowed with admirable antioxidant activity. Among the entire series compounds IP-9, IP-13 and IP-15 appeared as most active multi-functional agents and displayed marked AChE inhibitory, Aβ disaggregation and antioxidant activity. Studies indicate that IP-13 and IP-15 showed better AChE inhibitory activity than the standard drug donepezil and IP-9, IP-13 as well as IP-15 exhibited better Aβ aggregation inhibitory activity than curcumin. These compounds (IP-9, IP-13 and IP-15) successfully diminished H

Topics: Acetylcholine; Alzheimer Disease; Cell Line; Donepezil; Drug Delivery Systems; Drug Design; Humans; Indans; Ligands; Microscopy, Electron, Transmission; Molecular Dynamics Simulation; Molecular Structure; Neuroprotective Agents; Piperidines; Protein Aggregation, Pathological; Protein Binding

There are three specific regions in the Amyloid beta (Aβ) peptide sequence where variations cause enhanced toxicity in Alzheimer's disease: the N-terminus, the central salt bridge, and the C-terminus. Here, we investigate if there is a close conformational connection between these three regions, which may suggest a concerted mechanism of toxicity. We measure the effects of Zn

Topics: Amyloid; Amyloid beta-Peptides; Animals; Cations, Divalent; Cell Survival; Cells, Cultured; Cerebral Cortex; Curcumin; Microscopy, Electron, Transmission; Neurons; Neuroprotective Agents; Nuclear Magnetic Resonance, Biomolecular; Peptide Fragments; Protein Aggregation, Pathological; Protein Conformation; Rats; Spectrometry, Fluorescence; Zinc

The pathological aggregation of tau is a common feature of most of the neuronal disorders including frontotemporal dementia, Parkinson's disease, and Alzheimer's disease. The inhibition of tau aggregation is considered to be one of the important strategies for treating these neurodegenerative diseases. Curcumin, a natural polyphenolic molecule, has been reported to have neuroprotective ability. In this work, curcumin was found to bind to adult tau and fetal tau with a dissociation constant of 3.3±0.4 and 8±1 μM, respectively. Molecular docking studies indicated a putative binding site of curcumin in the microtubule-binding region of tau. Using several complementary techniques, including dynamic light scattering, thioflavin S fluorescence, 90° light scattering, electron microscopy, and atomic force microscopy, curcumin was found to inhibit the aggregation of tau. The dynamic light scattering analysis and atomic force microscopic images revealed that curcumin inhibits the oligomerization of tau. Curcumin also disintegrated preformed tau oligomers. Using Far-UV circular dichroism, curcumin was found to inhibit the β-sheets formation in tau indicating that curcumin inhibits an initial step of tau aggregation. In addition, curcumin inhibited tau fibril formation. Furthermore, the effect of curcumin on the preformed tau filaments was analyzed by atomic force microscopy, transmission electron microscopy, and 90° light scattering. Curcumin treatment disintegrated preformed tau filaments. The results indicated that curcumin inhibited the oligomerization of tau and could disaggregate tau filaments.

Topics: Circular Dichroism; Curcumin; Dynamic Light Scattering; Escherichia coli; Humans; Kinetics; Microscopy, Atomic Force; Microscopy, Electron; Molecular Docking Simulation; Neuroprotective Agents; Protein Aggregation, Pathological; Recombinant Proteins; Sequence Homology, Amino Acid; tau Proteins

Parkinson's disease is characterized by the presence of insoluble and neurotoxic aggregates (amyloid fibrils) of an intrinsically disordered protein α-synuclein. In this study we have examined the effects of four naturally occurring polyphenols in combination with β-cyclodextrin (β-CD) on the aggregation of α-synuclein in the presence of macromolecular crowding agents. Our results reveal that even at sub-stoichiometric concentrations of the individual components, the polyphenol-β-CD combination(s) not only inhibited the aggregation of the proteins but was also effective in disaggregating preformed fibrils. Curcumin was found to be the most efficient, followed by baicalein with (-)-epigallocatechin gallate and resveratrol coming in next, the latter two exhibiting very similar effects. Our results suggest that the efficiency of curcumin results from a balanced composition of the phenolic OH groups, benzene rings and flexibility. The latter ensures proper positioning of the functional groups to maximize the underlying interactions with both the monomeric form of α-synuclein and its aggregates. The uniqueness of β-CD was reinforced by the observation that none of the other cyclodextrin variants [α-CD and HP-β-CD] used was as effective, in spite of these possessing better water solubility. Moreover, the fact that the combinations remained effective under conditions of macromolecular crowding suggests that these have the potential to be developed into viable drug compositions in the near future. MTT assays on cell viability independently confirmed this hypothesis wherein these combinations (and the polyphenols alone too) appreciably impeded the toxicity of the prefibrillar α-synuclein aggregates on the mouse neuroblastoma cell lines (N2a cells).

Topics: alpha-Synuclein; Amyloid; Amyloidogenic Proteins; Animals; beta-Cyclodextrins; Catechin; Cell Line; Cell Survival; Circular Dichroism; Curcumin; Humans; Mice; Parkinson Disease; Polyphenols; Protein Aggregation, Pathological

A series of pterostilbene-O-acetamidoalkylbenzylamines were designed, synthesized and evaluated as dual inhibitors of AChE and BuChE. To further explore the multifunctional properties of the new derivatives, their antioxidant activities and inhibitory effects on self-induced Aβ1-42 aggregation and HuAChE-induced Aβ1-40 aggregation were also tested. The results showed that most of these compounds could effectively inhibit AChE and BuChE. Particularly, compound 21d exhibited the best AChE inhibitory activity (IC50=0.06 μM) and good inhibition of BuChE (IC50=28.04 μM). Both the inhibition kinetic analysis and molecular modeling study revealed that these compounds showed mixed-type inhibition, binding simultaneously to the CAS and PAS of AChE. In addition to cholinesterase inhibitory activities, these compounds showed different levels of antioxidant activity. However, the inhibitory activities against self-induced and HuAChE-induced Aβ aggregation of these new derivatives were unsatisfied. Taking into account the results of the biological evaluation, further modifications will be designed in order to increase the potency on the different targets. The results displayed in this Letter can be a new starting point for further development of multifunctional agents for Alzheimer's disease.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Antioxidants; Benzylamines; Butyrylcholinesterase; Cholinesterase Inhibitors; Cholinesterases; Dose-Response Relationship, Drug; Humans; Molecular Structure; Peptide Fragments; Protein Aggregates; Protein Aggregation, Pathological; Stilbenes; Structure-Activity Relationship

Protein aggregation underlies an array of human diseases, yet only one small-molecule therapeutic targeting this process has been successfully developed to date. Here, we introduce an in vivo system, based on a β-lactamase tripartite fusion construct, that is capable of identifying aggregation-prone sequences in the periplasm of Escherichia coli and inhibitors that prevent their aberrant self-assembly. We demonstrate the power of the system using a range of proteins, from small unstructured peptides (islet amyloid polypeptide and amyloid β) to larger, folded immunoglobulin domains. Configured in a 48-well format, the split β-lactamase sensor readily differentiates between aggregation-prone and soluble sequences. Performing the assay in the presence of 109 compounds enabled a rank ordering of inhibition and revealed a new inhibitor of islet amyloid polypeptide aggregation. This platform can be applied to both amyloidogenic and other aggregation-prone systems, independent of sequence or size, and can identify small molecules or other factors able to ameliorate or inhibit protein aggregation.

Topics: Amyloid beta-Peptides; beta-Lactamases; Biological Assay; Blotting, Western; Curcumin; Dopamine; Humans; Microscopy, Electron, Transmission; Protein Aggregation, Pathological; Protein Binding; Spectrometry, Mass, Electrospray Ionization

Experimental studies have shown that many naturally occurring polyphenols have inhibitory effect on the aggregation of several proteins. Here, we use discrete molecular dynamics (DMD) simulations and high-throughput dynamic light scattering (DLS) experiments to study the anti-aggregation effects of two polyphenols, curcumin and resveratrol, on the aggregation of islet amyloid polypeptide (IAPP or amylin). Our DMD simulations suggest that the aggregation inhibition is caused by stabilization of small molecular weight IAPP off-pathway oligomers by the polyphenols. Our analysis indicates that IAPP-polyphenol hydrogen bonds and π-π stacking combined with hydrophobic interactions are responsible for the stabilization of oligomers. The presence of small oligomers is confirmed with DLS measurements in which nanometer-sized oligomers are found to be stable for up to 7.5 hours, the time frame within which IAPP aggregates in the absence of polyphenols. Our study offers a general anti-aggregation mechanism for polyphenols, and further provides a computational framework for the future design of anti-amyloid aggregation therapeutics.

Topics: Aspirin; Curcumin; Hydrophobic and Hydrophilic Interactions; Islet Amyloid Polypeptide; Models, Molecular; Molecular Conformation; Nanostructures; Polyphenols; Protein Aggregates; Protein Aggregation, Pathological; Protein Binding; Resveratrol; Stilbenes

Tau is a key protein in the pathogenesis of various neurodegenerative diseases, which are categorized as tauopathies. Because the extent of tau pathologies is closely linked to that of neuronal loss and the clinical symptoms in Alzheimer's disease, anti-tau therapeutics, if any, could be beneficial to a broad spectrum of tauopathies. To learn more about tauopathy, we developed a novel transgenic nematode (Caenorhabditis elegans) model that expresses either wild-type or R406W tau in all the neurons. The wild-type tau-expressing worms exhibited uncoordinated movement (Unc) and neuritic abnormalities. Tau accumulated in abnormal neurites that lost microtubules. Similar abnormalities were found in the worms that expressed low levels of R406W-tau but were not in those expressing comparative levels of wild-type tau. Biochemical studies revealed that tau is aberrantly phosphorylated but forms no detergent-insoluble aggregates. Drug screening performed in these worms identified curcumin, a major phytochemical compound in turmeric, as a compound that reduces not only Unc but also the neuritic abnormalities in both wild-type and R406W tau-expressing worms. Our observations suggest that microtubule stabilization mediates the antitoxicity effect of curcumin. Curcumin is also effective in the worms expressing tau fragment, although it does not prevent the formation of tau-fragment dimers. These data indicate that curcumin improves the tau-induced neuronal dysfunction that is independent of insoluble aggregates of tau.

Topics: Animals; Animals, Genetically Modified; Caenorhabditis elegans; Curcumin; Disease Models, Animal; Gene Expression; Neurons; Protein Aggregation, Pathological; tau Proteins; Tauopathies

Spinal and bulbar muscular atrophy (SBMA, also known as Kennedy's disease) is one of nine neurodegenerative disorders that are caused by expansion of polyglutamine-encoding CAG repeats. Intracellular accumulation of abnormal proteins in these diseases, a pathological hallmark, is associated with defects in protein homeostasis. Enhancement of the cellular proteostasis capacity with small molecules has therefore emerged as a promising approach to treatment. Here, we characterize a novel curcumin analog, ASC-JM17, as an activator of central pathways controlling protein folding, degradation and oxidative stress resistance. ASC-JM17 acts on Nrf1, Nrf2 and Hsf1 to increase the expression of proteasome subunits, antioxidant enzymes and molecular chaperones. We show that ASC-JM17 ameliorates toxicity of the mutant androgen receptor (AR) responsible for SBMA in cell, fly and mouse models. Knockdown of the Drosophila Nrf1 and Nrf2 ortholog cap 'n' collar isoform-C, but not Hsf1, blocks the protective effect of ASC-JM17 on mutant AR-induced eye degeneration in flies. Our observations indicate that activation of the Nrf1/Nrf2 pathway is a viable option for pharmacological intervention in SBMA and potentially other polyglutamine diseases.

Topics: Animals; Bulbo-Spinal Atrophy, X-Linked; Curcumin; Disease Models, Animal; DNA-Binding Proteins; Drosophila melanogaster; Drosophila Proteins; Gene Knockdown Techniques; Heat Shock Transcription Factors; Humans; Mice; Muscular Disorders, Atrophic; NF-E2-Related Factor 1; NF-E2-Related Factor 2; Oxidative Stress; Peptides; Proteasome Endopeptidase Complex; Protein Aggregation, Pathological; Protein Folding; Receptors, Androgen; Signal Transduction; Small Molecule Libraries; Transcription Factors; Trinucleotide Repeat Expansion

Parkinson's disease (PD) is the most widespread form of dementia where there is an age related degeneration of dopaminergic neurons in the substantia nigra region of the brain. Accumulation of α-synuclein (αS) protein aggregate, mitochondrial dysfunction, oxidative stress, and neuronal cell death are the pathological hallmarks of PD. In this context, amalgamation of curcumin and piperine having profound cognitive properties, and antioxidant activity seems beneficial. However, the blood-brain barrier (BBB) is the major impediment for delivery of neurotherapeutics to the brain. The present study involves formulation of curcumin and piperine coloaded glyceryl monooleate (GMO) nanoparticles coated with various surfactants with a view to enhance the bioavailability of curcumin and penetration of both drugs to the brain tissue crossing the BBB and to enhance the anti-parkinsonism effect of both drugs in a single platform. In vitro results demonstrated augmented inhibition of αS protein into oligomers and fibrils, reduced rotenone induced toxicity, oxidative stress, and apoptosis, and activation of autophagic pathway by dual drug loaded NPs compared to native counterpart. Further, in vivo studies revealed that our formulated dual drug loaded NPs were able to cross BBB, rescued the rotenone induced motor coordination impairment, and restrained dopaminergic neuronal degeneration in a PD mouse model.

Topics: Alkaloids; alpha-Synuclein; Animals; Antiparkinson Agents; Benzodioxoles; Blood-Brain Barrier; Capillary Permeability; Curcumin; Drug Delivery Systems; Drug Therapy, Combination; Liposomes; Male; Mice, Inbred BALB C; Mice, Inbred C57BL; Nanoparticles; Neuroprotective Agents; Parkinsonian Disorders; PC12 Cells; Piperidines; Polyunsaturated Alkamides; Protein Aggregation, Pathological; Random Allocation; Rats; Rotenone; Surface-Active Agents

Amyloid fibrils are highly ordered protein aggregates associated with many diseases affecting millions of people worldwide. Polyphenols such as Curcumin, Exifone, and Myricetin exhibit modest inhibition toward fibril formation of tau peptide which is associated with Alzheimer's disease. However, the molecular mechanisms of this inhibition remain elusive. We investigated the binding of three polyphenol molecules to the protofibrils of an amyloidogenic fragment VQIVYK of tau peptide by molecular dynamics simulations in explicit solvent. We find that polyphenols induce conformational changes in the oligomer aggregate. These changes disrupt the amyloid H bonding, perturbing the aggregate. While the structural evolution of the control oligomer with no ligand is limited to the twisting of the β-sheets without their disassembly, the presence of polyphenol molecule pushes the β-sheets apart, and leads to a loosely packed structure where two of four β-sheets dissociate in each of the three cases considered here. The H-bonding capacity of polyphenols is responsible for the observed behavior. The calculated binding free energies and its individual components enabled better understanding of the binding. Results indicated that the contribution from Van der Waals interactions is more significant than electrostatic contribution to the binding. The findings from this study are expected to assist in the development of aggregation inhibitors. Significant binding between polyphenols and aggregate oligomer identified in our simulations confirms the previous experimental observations in which polyphenols refold the tau peptide without forming covalent bonds.

Topics: Amino Acid Sequence; Amyloid; Benzophenones; Curcumin; Flavonoids; Humans; Hydrogen Bonding; Models, Molecular; Molecular Conformation; Molecular Dynamics Simulation; Peptide Fragments; Polyphenols; Protein Aggregation, Pathological; Protein Binding; Protein Multimerization; Quantitative Structure-Activity Relationship; tau Proteins

Recent evidence supports the amyloid cascade hypothesis that a pathological change of amyloid β (Aβ) in the brain is an initiating event in Alzheimer's disease (AD). Accordingly, modulating the abnormal Aβ aggregation is considered a potential therapeutic target in AD. Curcumin, a low-molecular-weight polyphenol derived from the well-known curry spice turmeric, has shown favorable effects on preventing or treating AD pathology. The present study investigated the effects of curcumin and 2 novel curcumin derivatives, FMeC1 and FMeC2, on AD pathology in APPswe/PS1dE9 double transgenic mice. Mice fed a chow diet that contained FMeC1 for 6 months showed a reduction in insoluble Aβ deposits and glial cell activity together with reduced cognitive deficits, compared to animals receiving a control diet or with curcumin or FMeC2 in their diet. Both curcumin and FMeC1 modulated the formation of Aβ aggregates; however, only FMeC1 significantly attenuated the cell toxicity of Aβ. These results indicate that FMeC1 may have potential for preventing AD.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Brain; Cognition; Curcumin; Mice, Inbred C57BL; Mice, Transgenic; Molecular Targeted Therapy; Neuroglia; Presenilin-1; Protein Aggregation, Pathological

Clinical application of curcumin for Alzheimer's disease treatment is severely limited with regard to its poor bioavailability, high rate of metabolism, and instability under neutral condition. In the current study, we designed three compounds in which the diketone moiety of curcumin was replaced by cyclohexanone. In these compounds, the linker length of the molecules was optimal; and substitution of dioxolane for hydroxyl groups on compound 3 should prevent metabolic inactivation. The inhibitory effect of the compounds was investigated against hen egg white lysozyme (HEWL) fibrillation using AFM (atomic force microscope), ThT (thioflavin T) and MTT assay. We found that all three compounds were able to inhibit HEWL aggregation in a dose-dependent manner and inhibit the cytotoxic activity of aggregated HEWL. Docking results demonstrated that the compounds could bind into lysozyme and occupy the whole active site groove. In conclusion, we present chemical analogs of curcumin with various modifications in the spacer and the phenolic rings as improved inhibitors of amyloid aggregation.

Topics: Amyloid; Cell Line, Tumor; Cell Survival; Curcumin; Humans; Microscopy, Atomic Force; Models, Molecular; Molecular Conformation; Molecular Structure; Muramidase; Protein Aggregation, Pathological; Protein Binding; Spectrophotometry, Ultraviolet

Accumulating evidence suggests that deposition of neurotoxic α-synuclein aggregates in the brain during the development of neurodegenerative diseases like Parkinson's disease can be curbed by anti-aggregation strategies that either disrupt or eliminate toxic aggregates. Curcumin, a dietary polyphenol exhibits anti-amyloid activity but the use of this polyphenol is limited owing to its instability. As chemical modifications in curcumin confiscate this limitation, such efforts are intensively performed to discover molecules with similar but enhanced stability and superior properties. This study focuses on the inhibitory effect of two stable analogs of curcumin viz. curcumin pyrazole and curcumin isoxazole and their derivatives against α-synuclein aggregation, fibrillization and toxicity. Employing biochemical, biophysical and cell based assays we discovered that curcumin pyrazole (3) and its derivative N-(3-Nitrophenylpyrazole) curcumin (15) exhibit remarkable potency in not only arresting fibrillization and disrupting preformed fibrils but also preventing formation of A11 conformation in the protein that imparts toxic effects. Compounds 3 and 15 also decreased neurotoxicity associated with fast aggregating A53T mutant form of α-synuclein. These two analogues of curcumin described here may therefore be useful therapeutic inhibitors for the treatment of α-synuclein amyloidosis and toxicity in Parkinson's disease and other synucleinopathies.

Topics: alpha-Synuclein; Curcumin; Dose-Response Relationship, Drug; Humans; Kinetics; Models, Biological; Mutation; Neurodegenerative Diseases; Protein Aggregates; Protein Aggregation, Pathological; Protein Binding; Protein Multimerization; Structure-Activity Relationship

Small molecule based therapeutic intervention of amyloids has been limited by their low solubility and poor pharmacokinetic characteristics. We report here, the use of water soluble poly lactic-co-glycolic acid (PLGA)-encapsulated curcumin and emetine nanoparticles (Cm-NPs and Em-NPs, respectively), as potential modulators of gelsolin amyloidogenesis. Using the amyloid-specific dye Thioflavin T (ThT) as an indicator along with electron microscopic imaging we show that the presence of Cm-NPs augmented amyloid formation in gelsolin by skipping the pre-fibrillar assemblies, while Em-NPs induced non-fibrillar aggregates. These two types of aggregates differed in their morphologies, surface hydrophobicity and secondary structural signatures, confirming that they followed distinct pathways. In spite of differences, both these aggregates displayed reduced toxicity against SH-SY5Y human neuroblastoma cells as compared to control gelsolin amyloids. We conclude that the cytotoxicity of gelsolin amyloids can be reduced by either stalling or accelerating its fibrillation process. In addition, Cm-NPs increased the fibrillar bulk while Em-NPs defibrillated the pre-formed gelsolin amyloids. Moreover, amyloid modulation happened at a much lower concentration and at a faster rate by the PLGA encapsulated compounds as compared to their free forms. Thus, besides improving pharmacokinetic and biocompatible properties of curcumin and emetine, PLGA conjugation elevates the therapeutic potential of both small molecules against amyloid fibrillation and toxicity.

Topics: Amino Acid Sequence; Amyloidogenic Proteins; Cell Line; Curcumin; Emetine; Gelsolin; Humans; Hydrophobic and Hydrophilic Interactions; Kinetics; Lactic Acid; Models, Molecular; Molecular Sequence Data; Nanoparticles; Particle Size; Polyglycolic Acid; Polylactic Acid-Polyglycolic Acid Copolymer; Protein Aggregation, Pathological; Protein Conformation

In recent years, there has been growing interest in the near-infrared (NIR) fluorescence imaging of tau fibrils for the early diagnosis of Alzheimer's disease (AD). In order to develop a curcumin-based NIR fluorescent probe for tau fibrils, structural modification of the curcumin scaffold was attempted by combining the following rationales: the curcumin derivative should preserve its binding affinity to tau fibrils, and, upon binding to tau fibrils, the probe should show favorable fluorescence properties. To meet these requirements, we designed a novel curcumin scaffold with various aromatic substituents. Among the series, the curcumin derivative with a (4-dimethylamino-2,6-dimethoxy)phenyl moiety showed a significant change in its fluorescence properties (22.9-fold increase in quantum yield; Kd, 0.77 μM; λem, 620 nm; Φ, 0.32) after binding to tau fibrils. In addition, fluorescence imaging of tau-green fluorescent protein-transfected SHSY-5Y cells with confirmed that detected tau fibrils in live cells.

Topics: Alzheimer Disease; Cell Line; Curcumin; Fluorescent Dyes; Humans; Microscopy, Confocal; Molecular Probes; Optical Imaging; Protein Aggregation, Pathological; Spectrophotometry, Infrared; tau Proteins