In vitro investigation of the effect of mesalazine on amyloid fibril formation of hen egg-white lysozyme and defibrillation lysozyme fibrils

Polymeric Nanodiscs Comprising 5-Fluorouracil for Inhibition of Protein Aggregation and Their Anti-Alzheimer's Activity in the Drosophila Model

Nanoconjugates are promising for therapeutic drug delivery and targeted applications due to the numerous opportunities to functionalize their surface. The present study reports the synthesis of 5-fluorouracil (5-FU)-entrapped polyvinylpyrrolidone (PVP) nanoconjugates, precisely 5-FU-PVP and 5-FU-PVP-Au, and the evaluation of protein aggregation inhibition efficiency. The 5-FU-loaded polymer nanoconjugates were functionalized with gold nanoparticles and analyzed using characterization techniques like dynamic light scattering, UV-visible spectroscopy, Fourier-transform infrared spectroscopy, and zeta potential analysis. These conjugates exhibit consistent morphology with a spherical, flat, disc-like structure. The 5-FU-PVP and 5-FU-PVP-Au nanoconjugates exhibited a high drug loading, up to 81% and 90%, respectively. The nanoconjugates exhibited prolonged drug delivery of 5-FU from 5-FU-PVP and 5-FU-PVP-Au, wherein 5-FU-PVP-Au depicted a higher drug release. They were investigated for inhibiting the protein hen egg white lysozyme (HEWL) aggregation by ThT fibril size measurement, binding assay, and electron microscopy, and the results showed that conjugates repressed the fibrillogenesis in HEWL. The prominent activity of amyloid aggregation inhibition for HEWL using 5-FU-PVP and 5-FU-PVP-Au was found to be 29 μg.mL-1 and 27 μg.mL-1, respectively. The dissociation of amyloid aggregates was achieved against 5-FU-PVP and 5-FU-PVP-Au at 27 μg.mL-1 and 25 μg.mL-1, respectively. Furthermore, the nanoconjugates were investigated for anti-Alzheimer's activity in the Drosophila model. A Drosophila model of Alzheimer's disease (AD) was developed that expressed Aβ42 peptides in the neuronal secretory system to comprehend the pathogenic effects of Aβ42 in vivo. All the results demonstrate that polymer nanoconjugates exhibit more effective inhibition of protein aggregation than bare drugs.

Coomassie Brilliant Blue Induces Coiled-Coil Aggregation in Lysozyme at pH 7.4 by Hydrophobic and Electrostatic Forces

Several neurodegenerative diseases are associated with the deposition of amyloid fibrils. Although these diseases are irreversible, knowing the aggregation mechanism is useful in developing drugs that can arrest or decrease the aggregation rate. In this study, we are interested in investigating the effect of Coomassie brilliant blue (CBB G-250) on the aggregation of hen egg white lysozyme (HEWL) at pH 7.4. Various biophysical techniques have been used, such as turbidity, Rayleigh light scattering (RLS) kinetics, far-UV circular dichroism (CD), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM) imaging. The turbidity data indicated that CBB (≥0.1 mM) induces aggregation in HEWL at pH 7.4. The aggregation kinetics caused by CBB are quick without a lag phase and are dependent on the CBB concentration. The far-UV CD data revealed that the CBB-induced aggregated samples had lost their CD signals without exhibiting a shift in the spectrum position. Sodium chloride and ammonium sulfate show little effect on the CBB-induced aggregates, but alcohol such as methanol, ethanol, and 2-propanol could reverse the aggregation. Overall, this study aims to better understand the mechanism underlying CBB-induced aggregation and keep in mind that CBB employed in laboratories can alter the protein structure. We report the aggregation of a natural protein due to coiled-coil formation induced by a dye at physiological pH and temperature conditions. This finding has high value because several dyes are used for diagnostic and therapeutic purposes, and coiled-coil formation is closely related to infection mechanisms and nanoparticle-based drug deliveries.

Dissimilar effects of the hydrophilic carbon dots on the amyloid aggregation of two model proteins and the mechanism discussion

Many proteins could aggregate into amyloid fibrils under certain conditions. However, the aggregation process and morphology of the fibrils may be significantly different because of the distinct protein structure. In this article, the hydrophilic carbon dots (Lys-CA-CDs) were prepared using lysine (Lys) and citric acid (CA) as reactant under the assistance of a microwave. The dissimilar modulation effect of Lys-CA-CDs on the aggregation process of distinct structure protein was further investigated, where bovine serum albumin (BSA) and hen egg white lysozyme (HEWL) were chosen as model proteins. All results showed that Lys-CA-CDs displayed the contrary influence on the aggregation process of BSA and HEWL. Lys-CA-CDs could induce BSA to aggregate into more wormlike fibrils and inhibit the aggregation of HEWL into hair-like fibrils. The influence on the aggregation process of BSA may be assigned to the increased concentration of BSA around the Lys-CA-CDs caused by their interaction. However, inserting of Lys-CA-CDs into the inner structure of HEWL led to the change of protein secondary structure. The change of secondary structure further made it difficult for HEWL to aggregate into fibrils and Lys-CA-CDs showed the inhibition effect on HEWL aggregation.

Redesigning the kinetics of lysozyme amyloid aggregation by cephalosporin molecules

In lysozyme amyloidosis, fibrillar aggregates of lysozyme are associated with severe renal, hepatic, and gastrointestinal manifestations, with no definite therapy. Current drugs are now being tested in amyloidosis clinical trials as aggregation inhibitors to mitigate disease progression. The tetracycline group among antimicrobials in use is in phase II of clinical trials, whereas some macrolides and cephalosporins have shown neuroprotection. In the present study, two cephalosporins, ceftazidime (CZD) and cefotaxime (CXM), and a glycopeptide, vancomycin (VNC), are evaluated for inhibition of amyloid aggregation of hen egg white lysozyme (HEWL) under two conditions (i) 4 M guanidine hydrochloride (GuHCl) at pH 6.5 and 37° C, (ii) At pH 1.5 and 65 °C. Fluorescence quench titration and molecular docking methods report that CZD, CXM, and VNC interact more strongly with the partially folded intermediates (PFI) in comparison to the protein's natural state (N). However, only CZD and CXM proficiently inhibit the aggregation. Transmission electron microscopy, tinctorial assessments, and aggregation kinetics all support oligomer-level inhibition. Transition structures in CZD-HEWL and CXM-HEWL aggregation are shown by circular dichroism (CD). On the other hand, kinetic variables and soluble fraction assays point to a localized association of monomers. Intrinsic fluorescence (IF),1-Anilino 8-naphthalene sulphonic acid, and CD demonstrate structural and conformational modifications redesigning the PFI. GuHCl-induced unfolding and differential scanning fluorimetry suggested that the PFI monomers bound to CZD and CXM exhibited partial stability. Our results present two mechanisms that function in both solution conditions, creating a novel avenue for the screening of putative inhibitors for drug repurposing. We extend our proposed mechanisms in the designing of physical inhibitors of amyloid aggregation considering shorter time frames and foolproof methods.

Aggregation of gold nanoclusters in amyloid fibers: a luminescence assay for amyloid fibrillation detection and inhibitor screening

Amyloid fibrillation is associated with a great variety of human diseases, such as Alzheimer's and Huntington's diseases. A fluorescence assay for amyloid fibrillation detection and inhibitor screening was developed based on the fact that the fluorescence emission of gold nanoclusters (Au NCs) is largely enhanced upon adding amyloids, such as lysozyme amyloid fibers. A good linear relationship exists between the enhanced fluorescence intensity of Au NCs and lysozyme fiber within the concentration range of 0-0.05 mg mL-1. This ultra-sensitive method can detect the protein fiber earlier than thioflavin T (THT), allowing more time for disease treatment. Furthermore, Au NCs have many advantages over the classical probe (i.e., THT), such as large Stokes shifts and low toxicity. We selected ascorbic acid as a representative inhibitor and used this method to screen inhibitors. If inhibitors are added when incubating lysozyme, the lysozyme fibrosis process will be crimped, decreasing the amount of lysozyme fibers.

Manganese Ion-Induced Amyloid Fibrillation Kinetics of Hen Egg White-Lysozyme in Thermal and Acidic Conditions

As manganese ions (Mn²⁺) are identified as an environmental risk factor for neurodegenerative diseases, uncovering their action mechanism on protein amyloid fibril formation is crucial for related disease treatments. Herein, we performed a combined study of Raman spectroscopy, atomic force microscopy (AFM), thioflavin T (ThT) fluorescence, and UV-vis absorption spectroscopy assays, in which the distinctive effect of Mn²⁺ on the amyloid fibrillation kinetics of hen egg white-lysozyme (HEWL) was clarified at the molecular level. With thermal and acid treatments, the unfolding of protein tertiary structures is efficiently accelerated by Mn²⁺ to form oligomers, as indicated by two Raman markers for the Trp residues on protein side chains: the FWHM at 759 cm^-1 and the I₁₃₄₀/I₁₃₆₀ ratio. Meanwhile, the inconsistent evolutionary kinetics of the two indicators, as well as AFM images and UV-vis absorption spectroscopy assays, validate the tendency of Mn²⁺ toward the formation of amorphous aggregates instead of amyloid fibrils. Moreover, Mn²⁺ plays an accelerator role in the secondary structure transition from α-helix to organized β-sheet structures, as indicated by the N-C_α-C intensity at 933 cm^-1 and the amide I position of Raman spectroscopy and ThT fluorescence assays. Notably, the more significant promotion effect of Mn²⁺ on the formation of amorphous aggregates provides credible clues to understand the fact that excess exposure to manganese is associated with neurological diseases^.

Insights into the remarkable attenuation of hen egg white lysozyme amyloid fibril formation mediated by biogenic gold nanoparticles stabilized by quercetin-functionalized tara gum

Aberrant protein misfolding and/or aggregation and fibrillation has been linked to the pathogenesis of several debilitating chronic diseases including Alzheimer's and Parkinson's disease. Inhibiting protein amyloidogenesis has been proposed as a viable strategy to prevent or ameliorate associated disorders. Herein, we investigated the anti-amyloidogenic properties of biogenic gold nanoparticles (QTG-GNP) prepared via a simple green chemistry route and stabilized by quercetin-functionalized tara gum (QTG). The synthesized QTG-GNP was extensively characterized for its physicochemical attributes via UV-visible spectroscopy, TEM, FESEM, EDX, DLS/Zeta potential, FTIR, RAMAN, XRD, XPS, and TGA analyses, as well as for its biological properties. The results revealed that small-sized (5.01 ± 1.17 nm), well-dispersed, highly stable and round-shaped biogenic gold nanoparticles were successfully synthesized at room temperature with QTG as the sole reductant /stabilizer. Importantly, QTG-GNP demonstrated potent anti-aggregation and fibrillation inhibitory effects against amyloidogenic hen egg white lysozyme (HEWL). Also, QTG-GNP was able to dissociate pre-formed HEWL amyloid fibrils. Furthermore, the constructed nanoparticles exhibited potent anti-radical activities against DPPH and ABTS⁺ and were cytocompatible with mouse L929 fibroblast cells. On the basis of these findings, it was established that QTG-GNP holds strong prospects for further development as an agent for countering protein aggregation and associated disease conditions.

Mesalazine Inhibits Amyloid Formation and Destabilizes Pre-formed Amyloid Fibrils in the Human Insulin

Amyloid formation due to protein aggregation is associated with several amyloid diseases (amyloidosis). The use of small organic ligands as inhibitors of protein aggregation is an attractive strategy for the treatment of these diseases. In the present study, we evaluated the in vitro inhibitory and destabilizing effects of Mesalazine on human insulin fibrillation. To induce fibrillation, human insulin was incubated in 50 mM glycine buffer (pH 2.0) at 50 °C. The effect of Mesalazine on insulin amyloid aggregation was studied using spectroscopic, imaging, and computational approaches. Based on the results, the Mesalazine in a concentration-dependent manner (different ratios (1:0.1, 1:0.5, 1:1, and 1:5) of the insulin to Mesalazine) prevented the formation of amyloid fibrils and destabilized pre-formed fibrils. In addition, our molecular docking study confirmed the binding of Mesalazine to insulin through hydrogen bonds and hydrophobic interactions. Our findings suggest that Mesalazine may have therapeutic potential in the prevention of insulin amyloidosis and localized amyloidosis.

Anti-amyloidogenic property of gold nanoparticle decorated quercetin polymer nanorods in pH and temperature induced aggregation of lysozyme

Quercetin is an abundant plant polyphenol effective against several diseases due to its antioxidant and anti-inflammatory activity. Herein, we report novel polymeric quercetin nanorods and the former decorated with gold nanoparticles for the first time. The prepared conjugates quercetin-polyvinylpyrrolidone (Q-PVP) and quercetin-polyvinylpyrrolidone-gold nanoparticles (Q-PVP-Au) were characterized by UV-visible spectroscopy, Fourier transform infrared, dynamic light scattering, and zeta potential measurements. The surface morphology of conjugates was analyzed by field emission scanning electron microscopy. These conjugates exhibit harmonized rod-like morphology with a narrow size distribution. Furthermore, the quercetin conjugates with nanorod morphology exhibited enhanced and prolonged drug release over a long period. The synthesized conjugates were investigated for lysozyme aggregation kinetics. ThT binding assay, fibril size measurement, and electron microscopy results revealed that conjugates could suppress fibrillogenesis in lysozyme. The highest amyloid aggregation inhibition activity (IC50) was obtained against Q-PVP and Q-PVP-Au at 32 μg mL-1 and 30 μg mL-1 respectively. The amyloid aggregate disintegration activity (DC50) obtained against Q-PVP and Q-PVP-Au was 27 μg mL-1 and 29 μg mL-1 respectively. The present quercetin conjugates exhibit enhanced bioavailability and stability. They were potent inhibitors of lysozyme aggregation that may find applications as a therapeutic agent in neurological diseases like Alzheimer's and Parkinson's.

Z-scan optical method complements the Thioflavin T assay for investigation of anti-Alzheimer's impact of polyphenols

Polyphenols are tremendously effective in eliminating the amyloid-beta aggregations, the main hallmark of Alzheimer's disease. In recent years various nano drugs and biomaterials based on polyphenolic compounds have been synthetized to treat or prevent Alzheimer's disease, and the main in-vitro approach to investigate the anti-Alzheimer's properties of materials, is Thioflavin T assay. In spite of being very helpful, it has some drawbacks and cannot guarantee the accuracy of data, specifically in case of polyphenolic compounds; thus, rendering accurate results requires utilizing other assays along with Thioflavin T. In this experiment, we introduced Z-scan technique as a complementary test for Thioflavin T assay. In this study, the anti-Alzheimer's properties of two polyphenols quercetin and fulvic acid were assessed in the presence and absences of silver nanoparticles at various concentrations, both via Z-scan technique and Thioflavin T assay, after which the two tests were aligned with each other. The polyphenols' non-linear refractive indices obtained by the Z-scan technique correlated well with their related fluorescence intensities from the Thioflavin T assay in such a way that, the smaller the magnitude of the non-linear refractive indices, the stronger the anti-amyloidogenic impact. Our work shows that Z-scan could be used along with Thioflavin T for better investigation of polyphenols' anti-Alzheimer's properties.

A review of the biological and pharmacological activities of mesalazine or 5-aminosalicylic acid (5-ASA): an anti-ulcer and anti-oxidant drug

Mesalazine, also known as 5-aminosalicylic acid (5-ASA), is a synthetic drug from the family of nonsteroidal anti-inflammatory drugs (NSAIDs) used for inflammatory diseases of the gastrointestinal tract. However, 5-ASA has also been used for various other diseases due to its pharmacological effects, but they are usually scattered across various publications, which may limit further research and clinical use of this drug. This review is a summary of published information on the biological and pharmacological effects of 5-ASA with the aim of identifying its anti-oxidant role and medicinal use. 5-ASA data have been collected from 1987 to February 2021 using major databases such as Web of Science, PubMed, Elsevier, Wiley Online Library, Springer, Google Scholar, etc. According to research, the pharmacological and biological effects of 5-ASA include treatment of inflammatory bowel disease, and anti-oxidant, anti-inflammatory, antibacterial, antifungal, anticancer, anti-amyloid, gastric protection (gastroprotective), and antidiverticulosis properties. Numerous pharmacological studies have shown that 5-ASA is an anti-oxidant and anti-ulcer compound with high therapeutic potential that, if the appropriate dose is discovered, its chemical structure changes and its effectiveness is optimized, 5-ASA has been used experimentally for other diseases.