curcumin and Amyloidosis

Amyloidosis is a concept that implicates disorders and complications that are due to abnormal protein accumulation in different cells and tissues. Protein aggregation-associated diseases are classified according to the type of aggregates and deposition sites, such as neurodegenerative disorders and type 2 diabetes mellitus. Polyphenolic phytochemicals such as curcumin and its derivatives have anti-amyloid effects both in vitro and in animal models; however, the underlying mechanisms are not understood. In this review, we summarized possible mechanisms by which curcumin could interfere with self-assembly processes and reduce amyloid aggregation in amyloidosis. Furthermore, we discuss clinical trials in which curcumin is used as a therapeutic agent for the treatment of diseases linking to protein aggregates.

Topics: alpha-Synuclein; Alzheimer Disease; Amyloid beta-Peptides; Amyloidosis; Clinical Trials as Topic; Creutzfeldt-Jakob Syndrome; Curcumin; Diabetes Mellitus, Type 2; Humans; Huntington Disease; Hypoglycemic Agents; Mitochondria; Neuroprotective Agents; Oxidative Stress; Parkinson Disease; Protein Aggregates; tau Proteins

Progressive accumulation of misfolded amyloid proteins in intracellular and extracellular spaces is one of the principal reasons for synaptic damage and impairment of neuronal communication in several neurodegenerative diseases. Effective treatments for these diseases are still lacking but remain the focus of much active investigation. Despite testing several synthesized compounds, small molecules, and drugs over the past few decades, very few of them can inhibit aggregation of amyloid proteins and lessen their neurotoxic effects. Recently, the natural polyphenol curcumin (Cur) has been shown to be a promising anti-amyloid, anti-inflammatory and neuroprotective agent for several neurodegenerative diseases. Because of its pleotropic actions on the central nervous system, including preferential binding to amyloid proteins, Cur is being touted as a promising treatment for age-related brain diseases. Here, we focus on molecular targeting of Cur to reduce amyloid burden, rescue neuronal damage, and restore normal cognitive and sensory motor functions in different animal models of neurodegenerative diseases. We specifically highlight Cur as a potential treatment for Alzheimer's, Parkinson's, Huntington's, and prion diseases. In addition, we discuss the major issues and limitations of using Cur for treating these diseases, along with ways of circumventing those shortcomings. Finally, we provide specific recommendations for optimal dosing with Cur for treating neurological diseases.

Topics: Age Factors; Aging; Amyloid; Amyloidosis; Animals; Anti-Inflammatory Agents; Biological Products; Curcumin; Dose-Response Relationship, Drug; Drug Delivery Systems; Humans; Nanomedicine; Nanotechnology; Nerve Tissue; Neurodegenerative Diseases; Neuroprotective Agents; Polyphenols; Signal Transduction

Curcumin has attracted more attention because of its inhibition efficacy on protein amyloid fibrillation. However, the inhibition mechanism was still ambiguous and the clinical application of curcumin was greatly limited because of its poor stability at physiological conditions for the presence of β-diketone moiety. In this paper, a new mono-ketone-containing curcumin analogue (MDHC) was designed and synthesized to realize the possible inhibition mechanism and unveil the important role of β-diketone moiety of curcumin in the inhibition process of amyloid fibrillation using hen egg white lysozyme (HEWL) as model protein. Although all experiment results (ThT, CR, ANS and TEM) showed that the inhibitory capacity of curcumin was better than MDHC, MDHC still could show obvious inhibition effect. Molecular docking showed that both curcumin and MDHC could bind with HEWL by hydrogen bond of phenloic hydroxyl and the binding energy of MDHC was higher than that of curcumin. All the findings inferred that β-diketone group was one of great important groups in the inhibition process of HEWL amyloid fibrillation, which provided more room to construct novel inhibition reagents.

Topics: Amyloid; Amyloidogenic Proteins; Amyloidosis; Animals; Chick Embryo; Curcumin; Egg White; Molecular Docking Simulation; Muramidase

β-wrapins are engineered binding proteins of which different mutants can bind and sequester amyloidogenic proteins amyloid-β (Aβ), islet amyloid polypeptide (IAPP), and α-synuclein (α-syn), thereby inhibiting their aggregation into amyloid fibrils. β-wrapin AS10 is capable of binding and sequestering all three amyloidogenic monomers with micro-molar affinity, with its N-terminal domains remaining flexible and non-functional. Here, we computationally investigated the hypothesis that the anti-amyloid properties of AS10 can be amplified by redesigning its currently non-functional N-terminal domain with particular combinations of canonical and non-canonical amino acids (ncAAs) that can mimic the binding and inhibitory anti-amyloid function of curcumin, using a combination of molecular docking and molecular dynamics simulations. Our simulations suggest that the inhibitory mechanism attributed to the binding of the computationally designed AS10 N-terminal domain to the Aβ fibril can act simultaneously to its sequestering properties for Aβ which are attributed to the core of AS10. Thus, our study proposes that the N-terminal domain of AS10 can be further modified to amplify its anti-amyloid properties, resulting in a β-wrapin that may simultaneously prohibit elongation to existing amyloid fibrils and also sequester amyloid monomers.

Topics: Amino Acid Sequence; Amino Acids; Amyloid; Amyloid beta-Peptides; Amyloidogenic Proteins; Amyloidosis; Curcumin; Humans; Islet Amyloid Polypeptide; Molecular Docking Simulation

Some natural variants of human lysozyme are associated with systemic non-neurological amyloidosis that leads to amyloid protein fibril deposition in different tissues. Inhibition of amyloid fibrillation by nanomaterials is considered to be an effective approach to treating amyloidosis. Here, we prepared a targeted, highly loaded curcumin lysozyme-imprinted nanosphere (CUR-MIMS) that could effectively inhibit the aggregation of lysozyme with lysozyme adsorption capacity of 193.57 mg g

Topics: Amyloid; Amyloidogenic Proteins; Amyloidosis; Curcumin; Humans; Muramidase; Nanospheres

The effect of two widely used polyphenols, curcumin and EGCG was investigated on the amyloid fibrillogenesis of the well-characterized model protein human lysozyme (HuL), associated with non-neuropathic systemic amyloidosis, towards exploring their efficacy as modulators of HuL amyloid aggregation and toxicity and unravelling their mechanism of action. Curcumin exerts its inhibitory influence towards HuL fibrillation by interacting with the prefibrillar and fibrillar intermediates resulting in complete suppression of fibrillation at ∼200 µM and effectively disaggregates preformed fibrils of HuL. EGCG on the other hand suppresses fibrillation only upto 70% at ∼400 µM, modulates the pathway towards large, β-sheet rich amyloid fibril-like aggregates and modifies the preformed fibrils into similar type of large, clustered aggregate assemblies. The overall surface hydrophobicity and cytotoxicity of HuL is significantly reduced not only in the presence of curcumin but also EGCG, despite the latter forming large agglomerates, which could be accounted for by the dense and highly clustered nature of aggregates rendering their surface less exposed and thus less amenable to interact with cellular entities thereby causing reduced cellular toxicity. This study highlights the differential mechanisms employed by curcumin and ECCG in modulating the fibrillation pathway of HuL and illustrates the importance of overall modulation of fibrillation towards a general reduction in toxicity, rather than specifically focusing only on inhibition of fibrillation. This study also demonstrates how two widely different polyphenols employ disparate mechanisms to modulate the fibrillation pathway of a single protein and yet converge towards a common effect of alleviation of cytotoxicity.

Topics: Amyloid; Amyloidosis; Curcumin; Humans; Muramidase; Polyphenols

Curcumin is a polyphenol compound that exhibits multiple physiological activities. To elucidate the mechanisms by which curcumin affects systemic amyloidosis, we investigated amyloid deposition and molecular changes in a mouse model of amyloid apolipoprotein A-II (AApoAII) amyloidosis, in which mice were fed a curcumin-supplemented diet. Curcumin supplementation for 12 weeks significantly increased AApoAII amyloid deposition relative to controls, especially in the liver and spleen. Liver weights and plasma ApoA-II and high-density lipoprotein concentrations were significantly elevated in curcumin-supplemented groups. RNA-sequence analysis revealed that curcumin intake affected hepatic lipid metabolism via the peroxisome proliferator-activated receptor (PPAR) pathway, especially PPARα activation, resulting in increased

Topics: Amyloidosis; Animals; Apolipoprotein A-II; Curcumin; Female; Mice; Peroxisomes; PPAR alpha; Signal Transduction

Synaptic failure is one of the principal events associated with cognitive dysfunction in Alzheimer's disease (AD). Preservation of existing synapses and prevention of synaptic loss are promising strategies to preserve cognitive function in AD patients. As a potent natural anti-oxidant, anti-amyloid, and anti-inflammatory polyphenol, curcumin (Cur) shows great promise as a therapy for AD. However, hydrophobicity of natural Cur limits its solubility, stability, bioavailability, and clinical utility for AD therapy. We have demonstrated that solid lipid curcumin particles (SLCP) have greater therapeutic potential than natural Cur in vitro and in vivo models of AD. In the present study, we have investigated whether SLCP has any preservative role on affected dendritic spines and synaptic markers in 5xFAD mice.. Six- and 12-month-old 5xFAD and age-matched wild-type mice received oral administration of SLCP (100 mg/kg body weight) or equivalent amounts of vehicle for 2 months. Neuronal morphology, neurodegeneration, and amyloid plaque load were investigated from prefrontal cortex (PFC), entorhinal cortex (EC), CA1, CA3, and the subicular complex (SC). In addition, the dendritic spine density from apical and basal branches was studied by Golgi-Cox stain. Further, synaptic markers, such as synaptophysin, PSD95, Shank, Homer, Drebrin, Kalirin-7, CREB, and phosphorylated CREB (pCREB) were studied using Western blots. Finally, cognitive and motor functions were assessed using open-field, novel object recognition (NOR) and Morris water maze (MWM) tasks after treatment with SLCP.. We observed an increased number of pyknotic and degenerated cells in all these brain areas in 5xFAD mice and SLCP treatment partially protected against those losses. Decrease in dendritic arborization and dendritic spine density from primary, secondary, and tertiary apical and basal branches were observed in PFC, EC, CA1, and CA3 in both 6- and 12-month-old 5xFAD mice, and SLCP treatments partially preserved the normal morphology of these dendritic spines. In addition, pre- and postsynaptic protein markers were also restored by SLCP treatment. Furthermore, SLCP treatment improved NOR and cognitive function in 5xFAD mice.. Overall, these findings indicate that use of SLCP exerts neuroprotective properties by decreasing amyloid plaque burden, preventing neuronal death, and preserving dendritic spine density and synaptic markers in the 5xFAD mice.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Amyloidosis; Animals; Curcumin; Dendritic Spines; Disease Models, Animal; Guanine Nucleotide Exchange Factors; Hippocampus; Humans; Lipids; Mice; Mice, Transgenic

Many (poly-)phenolic natural products, for example, curcumin and taxifolin, have been studied for their activity against specific hallmarks of neurodegeneration, such as amyloid-β 42 (Aβ42) aggregation and neuroinflammation. Due to their drawbacks, arising from poor pharmacokinetics, rapid metabolism, and even instability in aqueous medium, the biological activity of azobenzene compounds carrying a pharmacophoric catechol group, which have been designed as bioisoteres of curcumin has been examined. Molecular simulations reveal the ability of these compounds to form a hydrophobic cluster with Aβ42, which adopts different folds, affecting the propensity to populate fibril-like conformations. Furthermore, the curcumin bioisosteres exceeded the parent compound in activity against Aβ42 aggregation inhibition, glutamate-induced intracellular oxidative stress in HT22 cells, and neuroinflammation in microglial BV-2 cells. The most active compound prevented apoptosis of HT22 cells at a concentration of 2.5 μm (83 % cell survival), whereas curcumin only showed very low protection at 10 μm (21 % cell survival).

Topics: Amyloid; Amyloid beta-Peptides; Amyloidosis; Curcumin; Humans; Oxidative Stress

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

Protein-derived amyloid structures are associated with a wide variety of pathologies, including neurodegenerative diseases and local amyloidoses. Reports exist on the ability of insulin to form local amyloidoses under specific conditions. In vitro-generated fibrils of insulin have been previously shown to produce amyloid-containing masses upon repetitive subcutaneous injection in mouse. The present study aimed at investigating the effect of insulin fibrils injection in rats, as well as the potential of turmeric in attenuating this process. It was found that subcutaneous amyloid-containing masses could form in rats at a faster rate compared with mice. Upon addition of turmeric to the fibrils, previous to injection, formed masses had a significantly reduced size, as well as less ordered cellular structure. In conclusion, the results of this study show the potential of turmeric in attenuation of local amyloidosis. Furthermore, we suggest that this model could be of use in screening antiamyloid compounds.

Topics: Amyloid; Amyloidosis; Animals; Curcuma; Curcumin; Injections, Subcutaneous; Insulin; Male; Microscopy, Fluorescence; Microscopy, Polarization; Rats, Wistar

Transthyretin amyloidoses encompass a variety of acquired and hereditary diseases triggered by systemic extracellular accumulation of toxic transthyretin aggregates and fibrils, particularly in the peripheral nervous system. Since transthyretin amyloidoses are typically complex progressive disorders, therapeutic approaches aiming multiple molecular targets simultaneously, might improve therapy efficacy and treatment outcome. In this study, we evaluate the protective effect of physiologically achievable doses of curcumin on the cytotoxicity induced by transthyretin oligomers in vitro by showing reduction of caspase-3 activity and the levels of endoplasmic reticulum-resident chaperone binding immunoglobulin protein. When given to an aged Familial Amyloidotic Polyneuropathy mouse model, curcumin not only reduced transthyretin aggregates deposition and toxicity in both gastrointestinal tract and dorsal root ganglia but also remodeled congophilic amyloid material in tissues. In addition, curcumin enhanced internalization, intracellular transport and degradation of transthyretin oligomers by primary macrophages from aged Familial Amyloidotic Polyneuropathy transgenic mice, suggesting an impaired activation of naïve phagocytic cells exposed to transthyretin toxic intermediate species. Overall, our results clearly support curcumin or optimized derivatives as promising multi-target disease-modifying agent for late-stage transthyretin amyloidosis.

Topics: Amyloid Neuropathies, Familial; Amyloidosis; Animals; Caspase 3; Cell Line, Tumor; Curcumin; Endoplasmic Reticulum; Prealbumin; Rats

More than twenty-seven human proteins can fold abnormally to form amyloid deposits associated with a number of degenerative diseases. The research reported here is aimed at exploring the connection between curcumin's thermostability and its inhibitory activity toward the amyloid fibrillation of hen egg-white lysozyme (HEWL).. ThT fluorescence spectroscopy, equilibrium thermal denaturation analysis, and transmission electron microscopy were employed for structural characterization. MTT reduction and flow cytometric analyses were used to examine cell viability.. The addition of thermally pre-treated curcumin was found to attenuate the formation of HEWL fibrils and the observed fibrillation inhibition was dependent upon the pre-incubation temperature of curcumin. Our results also demonstrated that the cytotoxic effects of fibrillar HEWL species on PC 12 and SH-SY5Y cells were decreased and negatively correlated with curcumin's thermostability. Next, an enhanced stability of HEWL was perceived upon the addition of curcumin pre-incubated at lower temperature. Furthermore, we found that the alteration of curcumin's thermostability was associated with its inhibitory potency against HEWL fibrillation.. We believe that the results from this research may contribute to the development of effective therapeutics for amyloidoses.

Topics: Amyloid; Amyloidosis; Animals; Cell Survival; Curcumin; Flow Cytometry; Muramidase; PC12 Cells; Protein Folding; Rats; Spectrophotometry, Ultraviolet; Temperature; Thermodynamics

In a previous in vitro study, the standardized turmeric extract, HSS-888, showed strong inhibition of Aβ aggregation and secretion in vitro, indicating that HSS-888 might be therapeutically important. Therefore, in the present study, HSS-888 was evaluated in vivo using transgenic 'Alzheimer' mice (Tg2576) over-expressing Aβ protein. Following a six-month prevention period where mice received extract HSS-888 (5mg/mouse/day), tetrahydrocurcumin (THC) or a control through ingestion of customized animal feed pellets (0.1% w/w treatment), HSS-888 significantly reduced brain levels of soluble (∼40%) and insoluble (∼20%) Aβ as well as phosphorylated Tau protein (∼80%). In addition, primary cultures of microglia from these mice showed increased expression of the cytokines IL-4 and IL-2. In contrast, THC treatment only weakly reduced phosphorylated Tau protein and failed to significantly alter plaque burden and cytokine expression. The findings reveal that the optimized turmeric extract HSS-888 represents an important step in botanical based therapies for Alzheimer's disease by inhibiting or improving plaque burden, Tau phosphorylation, and microglial inflammation leading to neuronal toxicity.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Amyloidosis; Analysis of Variance; Animals; Antioxidants; Curcuma; Cytokines; Disease Models, Animal; Enzyme-Linked Immunosorbent Assay; Humans; Mice; Mice, Transgenic; Mutation; Peptide Fragments; Phosphorylation; Plant Extracts; tau Proteins

Several natural polyphenols with potent inhibitory effects on amyloid fibril formation have been reported. Herein, we studied modulation of transthyretin (TTR) fibrillogenesis by selected polyphenols. We demonstrate that both curcumin and nordihydroguaiaretic acid (NDGA) bind to TTR and stabilize the TTR tetramer. However, while NDGA slightly reduced TTR aggregation, curcumin strongly suppressed TTR amyloid fibril formation by generating small "off-pathway" oligomers and EGCG maintained most of the protein in a non-aggregated soluble form. This indicates alternative mechanisms of action supported by the occurrence of different non-toxic intermediates. Moreover, EGCG and curcumin efficiently disaggregated pre-formed TTR amyloid fibrils. Our studies, together with the safe toxicological profile of these phytochemicals may guide a novel pharmacotherapy for TTR-related amyloidosis targeting different steps in fibrillogenesis.

Topics: Amyloid; Amyloidosis; Catechin; Curcumin; Flavonoids; Phenols; Polyphenols; Prealbumin; Protein Binding; Protein Multimerization

We identified a molten globule-like intermediate of 2,5-diketo-D-gluconate reductase A (DKGR) at pH 2.5, which has a prominent beta-sheet structure. The molten globule state of the protein shows amyloidogenic property >50 microm protein concentration. Interestingly, a 1:1 molar ratio of curcumin prevents amyloid formation as shown by the Thioflavin-T assay and atomic force microscopy. To the best of our knowledge, this is the first report on amyloid formation by an (alpha/beta)(8)-barrel protein. The results presented here indicate that the molten globule state has an important role in amyloid formation and potential application of curcumin in protein biotechnology as well as therapeutics against amyloid diseases.

Topics: Amyloid; Amyloidosis; Benzothiazoles; Biological Assay; Circular Dichroism; Curcumin; Hydrogen-Ion Concentration; Microscopy, Atomic Force; Protein Folding; Protein Structure, Secondary; Spectrometry, Fluorescence; Spectrophotometry, Ultraviolet; Sugar Alcohol Dehydrogenases; Thiazoles; Time Factors