Ellagic acid and pentagalloylglucose are potential inhibitors of prion protein fibrillization

Roles of Apigenin and Nepetin in the Assembly Behavior and Cytotoxicity of Prion Neuropeptide PrP106-126

Development of potential inhibitors to prevent prion protein (PrP) fibrillation is a therapeutic strategy for prion diseases. The prion neuropeptide PrP106-126, a research model of abnormal PrP (PrPSc), presents similar physicochemical and biochemical characters to PrPSc, which is also a target of potential inhibitors against prion deposition. Many flavones have antioxidant, anti-inflammatory, and antibacterial properties, and they are applied in treating prion disorder and other amyloidosis as well. However, the inhibition mechanism of flavones on PrP106-126 fibrillation is still unclear. In the current work, apigenin and nepetin were used to suppress the aggregation of PrP106-126 and to alleviate the peptide-induced cytotoxicity. The results showed that apigenin and nepetin impeded the fibril formation of PrP106-126 and depolymerized the preformed fibrils. They were bound to PrP106-126 predominantly by hydrophobic and hydrogen bonding interactions. In addition, both flavones upregulated cell viability and decreased membrane leakage through reducing peptide oligomerization. The differences in inhibition and cell protection between the two small molecules were presumably attributed to the substitution of hydroxyl and methoxy groups in nepetin, which demonstrated the significant structure-function relationship of flavones with prion neuropeptide and the prospect of flavonoids as drug candidates against prion diseases.

Anti-amyloid potential of some phytochemicals against Aβ-peptide and α-synuclein, tau, prion, and Huntingtin protein

Some molecules self-assemble to create complex structures through molecular self-assembly. Hydrogel preparation, tissue repair, and therapeutic drug delivery are a few applications of molecular self-assembly. However, the self-assembly of amino acids, peptides, and proteins forms amyloid fibrils, resulting in various disorders, most notably neurodegenerative ailments. Examples include the self-assembly of phenylalanine, which causes phenylketonuria; Aβ, which causes Alzheimer's disease; the tau protein, which causes both Alzheimer's and Parkinson's diseases; and α-synuclein, which causes Parkinson's illness. This review provides information related to phytochemicals of great significance that can prevent the formation of, or destabilize, amino acid, peptide, and protein self-assemblies.

Binding modes of potential anti-prion phytochemicals to PrPC structures in silico

BACKGROUND

Prion diseases involve the conversion of a normal, cell-surface glycoprotein (PrPC) into a misfolded pathogenic form (PrPSc). One possible strategy to inhibit PrPSc formation is to stabilize the native conformation of PrPC and interfere with the conversion of PrPC to PrPSc. Many compounds have been shown to inhibit the conversion process, however, no promising drugs have been identified to cure prion diseases.

OBJECTIVE

This study aims to identify potential anti-prion compounds from plant phytochemicals by integrating traditional ethnobotanical knowledge with modern in silico drug design approaches.

MATERIALS AND METHODS

In the current study medicinal phytochemicals were docked with swapped and non-swapped crystal structures of PrPCin silico to identify potential anti-prions to determine their binding modes and interactions.

RESULTS

Eleven new phytochemicals were identified based on their binding energies and pharmacokinetic properties. The binding sites and interactions of the known and new anti-prion compounds are similar, and differences in binding modes occur in structures with very subtle differences in side chain conformations. Binding of these compounds poses steric hindrance to neighbouring molecules. Residues shown to be associated with the inhibition of PrPC to PrPSc conversion form interactions with most of the compounds.

CONCLUSION

Identified compounds might act as potent inhibitors of PrPC to PrPSc conversion. These might be attractive candidates for the development of novel anti-prion therapy although further tests in vitro cell cultures and in vivo mouse models are needed to confirm these findings.

Inhibitory effects of sesquiterpene lactones on the aggregation and cytotoxicity of prion neuropeptide

The misfolding and conformational transformation of prion protein (PrP) are crucial to the progression of prion diseases. Screening for available natural inhibitors against prion proteins can contribute to the rational design and development of new anti-prion drugs and therapeutic strategies. The prion neuropeptide, PrP106-126 is commonly used as a model peptide of the abnormal PrP^Sc, and a number of potential inhibitors were explored against the amyloid fibril formation of PrP106-126. The well-known sesquiterpene lactone, artemisinin, shows diverse biological functions in anti-malarial, anti-cancer and lowering glucose. However, its inhibitory effect on PrP106-126 fibrillation is unclear. In this work, we selected two sesquiterpene lactones, artemisinin (1) and artesunate (2), to explore their roles in PrP106-126 aggregation by a series of physicochemical and biochemical methods. The results demonstrated that 1 and 2 could effectively impede the formation of amyloid fibrils and remodel the preformed fibrils. The binding of the small molecules to PrP106-126 was dominated by electrostatic, hydrophobic and hydrogen bonding interactions. In addition, both compounds exhibited neuroprotective effects by reducing peptide oligomerization. 2 showed better inhibition and regulation on peptide aggregation and cellular viability than 1 due to its specific succinate modification. Our study provides the information of sesquiterpene lactones to prevent PrP fibril formation and other related amyloidosis.

Study on the Mechanism of Baimai Ointment in the Treatment of Osteoarthritis Based on Network Pharmacology and Molecular Docking with Experimental Verification

Purpose: The external preparation of the Tibetan medicine formula, Baimai ointment (BMO), has great therapeutic effects on osteoarthritis (OA). However, its molecular mechanism remains almost elusive. Here, a comprehensive strategy combining network pharmacology and molecular docking with pharmacological experiments was adopted to reveal the molecular mechanism of BMO against OA. Methods: The traditional Chinese medicine for systems pharmacology (TCMSP) database and analysis platform, traditional Chinese medicine integrated database (TCMID), GeneCards database, and DisGeNET database were used to screen the active components and targets of BMO in treating OA. A component-target (C-T) network was built with the help of Cytoscape, and the Gene Ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment through STRING. Autodock Tools which was used to dock the key components and key target proteins was analyzed. Animal experiments were performed to verify the key targets of BMO. Hematoxylin-eosin and toluidine blue staining were used to observe the pathology of joints. Protein expression was determined using enzyme-linked immunosorbent assay. Results: Bioactive compounds and targets of BMO and OA were screened. The network analysis revealed that 17-β-estradiol, curcumin, licochalone A, quercetin, and glycyrrhizic acid were the candidate key components, and IL6, tumor necrosis factor (TNF), MAPK1, VEGFA, CXCL8, and IL1B were the candidate key targets in treating OA. The KEGG indicated that the TNF signaling pathway, NF-κB signaling pathway, and HIF-1 signaling pathway were the potential pathways. Molecular docking implied a strong combination between key components and key targets. The pathology and animal experiments showed BMO had great effects on OA via regulating IL6, TNF, MAPK1, VEGFA, CXCL8, and IL1B targets. These findings were consistent with the results obtained from the network pharmacology approach. Conclusion: This study preliminarily illustrated the candidate key components, key targets, and potential pathways of BMO against OA. It also provided a promising method to study the Tibetan medicine formula or external preparations.

Ellagic Acid Modulates Uninduced as well as Mutation and Metal-Induced Aggregation of α-Synuclein: Implications for Parkinson's Disease

α-Synuclein (αS) is an intrinsically disordered protein whose aggregation and deposition in Lewy bodies is involved in the progression of Parkinson's disease (PD) and other related disorders. The aggregation process of αS is also triggered by mutations like A53T and E46K in the SNCA gene and disruption in metal-ion homeostasis. Currently, there is no obviating therapy available in the market that could effectively prevent the progression of the disease. In this backdrop, there exists an emerging need to consider naturally occurring polyphenols and flavonoids as potential therapeutic agents against PD. In this study, we demonstrate the modulatory effect of ellagic acid (EA) against wild-type as well as mutation and metal-induced aggregation of αS. Thioflavin T (ThT) fluorescence assay suggests that EA acts on the nucleation phase of αS fibrillization, thereby increasing the lag phase from 21.33 ± 3.01 to 48.20 ± 5.05 h and reducing the fibrils growth rate from 4.60 ± 2.06 to 0.890 ± 0.36 h^-1. 8-Anilino-1-naphthalene sulfonic acid (ANS), Congo red (CR), and intrinsic fluorescence studies indicate that the interaction of EA with αS facilitates the structural changes in the protein that lead to inhibition of fibril formation. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) images illustrate that the size of fibrils diminishes up to 100 nm in the presence of EA. Dot blot and seeding experiments put forward that EA directs the αS aggregation toward off-pathway fibrillization. Our 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay deciphers the role of EA in minimizing the αS fibril-induced toxicity, thereupon leading to an increase in cell viability. Also, EA attenuates both mutations as well as metal-induced αS fibrillization and disaggregates the preexisting fibrils. Additionally, computational studies elucidate that EA preferentially interacts with the N-terminal and NAC domain of αS. Hence, this work reveals the aggregation inhibition mechanism of EA and provides considerable therapeutic interventions against PD and related disorders.