Disaggregation Of Fibrils Research Articles

Design, Synthesis, Biological Evaluation and Docking Studies of 2-hydroxy-4-benzyloxy Chalcone Derivatives as Multifunctional Agents for the Treatment of Alzheimer's Disease.

Alzheimer's disease (AD) is the most prevalent neurodegenerative disorder, but no drugs can cure this disease. Chalcones possess good antioxidant activity, anti-neuroinflammatory activity, neuroprotective effects, inhibitory effects on Aβ aggregation, and Aβ disaggregation ability. Therefore, chalcones are ideal lead compounds, and the discovery of novel anti-AD agent-based chalcones is necessary. Hydroxy groups and aryl benzyl ether groups were introduced into chalcone scaffolds to obtain a series of 2-hydroxyl-4-benzyloxy chalcone derivatives. These derivatives were further synthesized, biologically evaluated, and docked. Most target derivatives exhibited good anti-AD activities. In particular, compound 11d had excellent inhibitory effects on self-induced Aβ1-42 aggregation (90.8% inhibition rate at 25 μM) and Cu2+ induced Aβ1-42 aggregation (93.4% inhibition rate at 25 μM). In addition, it also exhibited good Aβ1-42 fibril disaggregation ability (64.7% at 25 μM), significant antioxidative activity (ORAC = 2.03 Trolox equivalent), moderate MAO-B inhibition (IC50 = 4.81 μM), selective metal chelation, appropriate BBB permeation, and dramatic anti-neuroinflammatory ability. In addition, compound 11d relieved AD symptoms and protected hippocampal neurons in vivo. Compound 11d is a promising multifunctional anti-Aβ agent.

Exposed Hsp70-binding site impacts yeast Sup35 prion disaggregation and propagation

The dynamic balance between formation and disaggregation of amyloid fibrils is associated with many neurodegenerative diseases. Multiple chaperones interact with and disaggregate amyloid fibrils, which impacts amyloid propagation and cellular phenotypes. However, it remains poorly understood whether and how site-specific binding of chaperones to amyloids facilitates the concerted disaggregation process and modulates physiological consequences in vivo. Here, we identified binding sites of Ssa1, Sis1, and Hsp104 chaperones for Sup35, the protein determinant of yeast prion [PSI+] yeast. Our biophysical and genetic analyses with various Sup35 deletion mutants and amyloid conformations revealed that the Ssa1-binding to the region outside amyloid core plays a key role in facilitating disaggregation and propagation of yeast prions both in vitro and in vivo. Furthermore, we developed a reconstitution system, including the Ssa1-binding tag and the HAP/Caseinolytic protease P (ClpP) hybrid chaperones, and found that this reconstitution system successfully degraded distinct prion strain conformations. Together, these results show that the properly positioned, exposed Ssa1-binding region in amyloid fibrils influences the efficiency of amyloid disaggregation and propagation, and eventually prion strain phenotypes. More broadly, our findings provide molecular foundations for previous, puzzling observations of prion propagation in vivo, and offer insights into elimination of amyloid deposits in cells.

Photocatalytic, photothermal, and blood-brain barrier-permeable carbon nanodots: A potent multifunctional scavenger for β-amyloid plaque

Alzheimer’s disease (AD) is associated with amyloid production and buildup in the brain, leading to neurodegeneration. In this study, we used a solvent-thermal technique to produce light-sensitive carbon nanodots (L-CNDs). L-CNDs exhibit outstanding photocatalytic properties, producing singlet oxygen (1O2) under 630 nm irradiation. L-CNDs have a high photothermal conversion efficiency of 68.25 % under 808 nm irradiation, allowing for localized heating and regulation of Aβ aggregation. L-CNDs bind Aβ through hydrophobic interaction and π-π stacking. L-CNDs inhibit Aβ aggregation with efficiencies of 61.08 %, 75.09 %, and 91.72 % at 10 μg·mL−1 in photothermal therapy (PTT), photodynamic therapy (PDT), and PTT/PDT synergistic therapy, respectively. L-CNDs efficiently suppress Aβ misfolding, inhibit fibrillation, and promote disaggregation of mature fibrils. L-CNDs mitigate Aβ-induced cytotoxicity in PC12 and HT22 cells. Interestingly, the data showed that 84.6 % of the L-CNDs could penetrate bEnd.3 cells after 8 h of treatment, demonstrating that they have the capacity to cross the blood-brain barrier (BBB) because of their small size. In vitro investigations have shown that L-CNDs can pass through the BBB. Collectively, our findings reveal a unique technique for treating amyloid disorders using carbon nanodots with significant potential for future studies in this area.

CRBN modulates synuclein fibrillation via degradation of DNAJB1 in mouse model of Parkinson disease

Cereblon (CRBN) is a substrate recruiter for CRL4CRBN E3 ubiquitin ligase system playing a plethora of pivotal roles for biological systems. Here, we identified DNAJB1 (DJ1) as endogenous substrate of CRBN and report how CRBN influences the aggregation and toxicity of alpha-synuclein (α-SYN) via modulation of DJ1. CRBN interferes with molecular activities of DJ1 in vitro, in cells, and in vivo resulting in a reduced disaggregation of α-SYN fibrils, increased formation of preformed fibrils (PFFs) of α-SYN, and high susceptibility of mice to MPTP and PFF-induced neurotoxicity. Depletion of Crbn improves the behavioral and biochemical responses of mice towards neurotoxic insult. Finally, we designed a peptide inhibitor to inhibit the recruitment of DJ1 to CRBN for ubiquitination, resulting in an enhanced supply of DJ1 to counteract the toxicity of aggregated α-SYN. Our data has important implications for development of CRBN-targeting therapies that could prevent or delay progression of neurodegenerative synucleinopathy.

Exploring Tau Fibril-Disaggregating and Antioxidating Molecules Binding to Membrane-Bound Amyloid Oligomers Using Machine Learning-Enhanced Docking and Molecular Dynamics.

Intracellular tau fibrils are sources of neurotoxicity and oxidative stress in Alzheimer's. Current drug discovery efforts have focused on molecules with tau fibril disaggregation and antioxidation functions. However, recent studies suggest that membrane-bound tau-containing oligomers (mTCOs), smaller and less ordered than tau fibrils, are neurotoxic in the early stage of Alzheimer's. Whether tau fibril-targeting molecules are effective against mTCOs is unknown. The binding of epigallocatechin-3-gallate (EGCG), CNS-11, and BHT-CNS-11 to in silico mTCOs and experimental tau fibrils was investigated using machine learning-enhanced docking and molecular dynamics simulations. EGCG and CNS-11 have tau fibril disaggregation functions, while the proposed BHT-CNS-11 has potential tau fibril disaggregation and antioxidation functions like EGCG. Our results suggest that the three molecules studied may also bind to mTCOs. The predicted binding probability of EGCG to mTCOs increases with the protein aggregate size. In contrast, the predicted probability of CNS-11 and BHT-CNS-11 binding to the dimeric mTCOs is higher than binding to the tetrameric mTCOs for the homo tau but not for the hetero tau-amylin oligomers. Our results also support the idea that anionic lipids may promote the binding of molecules to mTCOs. We conclude that tau fibril-disaggregating and antioxidating molecules may bind to mTCOs, and that mTCOs may also be useful targets for Alzheimer's drug design.

Biosynthesis of Nanoparticles with Green Tea for Inhibition of β-Amyloid Fibrillation Coupled with Ligands Analysis.

Inhibition of amyloid β protein fragment (Aβ) aggregation is considered to be one of the most effective strategies for the treatment of Alzheimer's disease. (-)-Epigallocatechin-3-gallate (EGCG) has been found to be effective in this regard; however, owing to its low bioavailability, nanodelivery is recommended for practical applications. Compared to chemical reduction methods, biosynthesis avoids possible biotoxicity and cumbersome preparation processes. The interaction between EGCG and Aβ42 was simulated by molecular docking, and green tea-conjugated gold nanoparticles (GT-Au NPs) and EGCG-Au NPs were synthesized using EGCG-enriched green tea and EGCG solutions, respectively. Surface active molecules of the particles were identified and analyzed using various liquid chromatography-tandem triple quadrupole mass spectrometry methods. ThT fluorescence assay, circular dichroism, and TEM were used to investigate the effect of synthesized particles on the inhibition of Aβ42 aggregation. EGCG as well as apigenin, quercetin, baicalin, and glutathione were identified as capping ligands stabilized on the surface of GT-Au NPs. They more or less inhibited Aβ42 aggregation or promoted fibril disaggregation, with EGCG being the most effective, which bound to Aβ42 through hydrogen bonding, hydrophobic interactions, etc. resulting in 39.86% and 88.50% inhibition of aggregation and disaggregation effects, respectively. EGCG-Au NPs were not as effective as free EGCG, whereas multiple thiols and polyphenols in green tea accelerated and optimized heavy metal detoxification. The synthesized GT-Au NPs conferred the efficacy of diverse ligands to the particles, with inhibition of aggregation and disaggregation effects of 54.69% and 88.75%, respectively, while increasing the yield, enhancing water solubility, and decreasing cost. Biosynthesis of nanoparticles using green tea is a promising simple and economical drug-carrying approach to confer multiple pharmacophore molecules to Au NPs. This could be used to design new drug candidates to treat Alzheimer's disease.

Cyrene- and water-based exfoliation of black phosphorus for potential nanolayer-mediated disaggregation of insulin fibrils

Liquid suspensions of phosphorene nanolayers (2D-bP) obtained through liquid phase exfoliation (LPE) of elemental black phosphorus (bP) have been prepared and extensively characterized. The exfoliating ability of deionized water (DI water), dihydrolevoglucosenone, (Cyrene), and N-methyl-2-pyrrolidone (NMP) has been investigated and compared along with the differences in the structure, concentration, and stability of the collected nanoflakes. Water was chosen as an exfoliating medium due to its harmlessness and cost-effectiveness and because it is the safest solvent for further potential biomedical applications. Cyrene is a new bio-based solvent still under study. NMP, which is among the most widely used solvents for the exfoliation of 2D systems including bP, has been employed for comparison. The obtained suspensions have been characterized by Dynamic Light Scattering (DLS), Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES), Phosphorus 31 Nuclear Magnetic Resonance (31P NMR), Transmission Electron Microscopy (TEM), Ultraviolet -Visible (UV–Vis), and Raman spectroscopies. The stability of 2D-bP suspensions over time and their photoactivity, i.e., their ability to generate singlet oxygen species as a photosensitizer, have been investigated. The collected results evidenced that the exfoliation of bP in different solvents, including DI water, resulted in satisfactory and comparable nanoflake structures and features. The singlet oxygen generation through irradiation of 2D-bP in DI water suspensions, advantageously obtained directly from LPE, showed promising potential for use in photodynamic therapy (PDT). Preliminary data on the potential biomedical application of 2D-bP to inhibit the insulin self-assembly into amyloid aggregates as well as to cause fibrils disassembling through simple incubation or photoactivity, are also discussed.

A Peptide‐Polyphenol Coated Polypyrrole Nanoparticle for Synergetic Attenuation of Aggregation and Cytotoxicity of Amyloid‐β Fibrils

AbstractAmyloid‐β (Aβ) pathway is positioned as the center for Alzheimer's disease (AD) pathophysiology. Viable drugs targeting Aβ pathway are developed with promising outcomes. Meanwhile, most current approaches are focused on the inhibition of Aβ fibrillization or elimination of Aβ plaques by immunotherapeutic strategies. Here, near‐infrared (NIR) photothermal polypyrrole nanoparticles coated with peptide‐polyphenol are developed to both inhibit the Aβ fibrillization and disaggregate Aβ fibrils synergistically. Aβ fibrillization is obviously inhibited after being treated with the photothermal polypyrrole nanoparticles. Besides inhibition of Aβ fibrillization, the amount of Aβ fibrils is gradually reduced with time by 38.0% when co‐incubated with polypyrrole nanoparticles, indicating desired disaggregation capability against Aβ fibrils. In addition, faster and more disaggregation of Aβ fibrils is observed when irradiation by NIR light. Meanwhile, cellular studies also verified that this nanoparticle is able to effectively reduce the cytotoxicity of Aβ fibrils toward PC12 cells through disaggregating toxic Aβ aggregates and maintaining integral membrane structure. Hence, this peptide‐polyphenol‐coated NIR photothermal polypyrrole nanoparticle provides a new perspective for the inhibition of Aβ fibrillization and disaggregation of Aβ fibrils, which can serve as a promising approach for anti‐amyloidosis.

Natural compound plumbagin based inhibition of hIAPP revealed by Markov state models based on MD data along with experimental validations.

Human islet amyloid polypeptide (amylin or hIAPP) is a 37 residue hormone co-secreted with insulin from β cells of the pancreas. In patients suffering from type-2 diabetes, amylin self-assembles into amyloid fibrils, ultimately leading to the death of the pancreatic cells. However, a research gap exists in preventing and treating such amyloidosis. Plumbagin, a natural compound, has previously been demonstrated to have inhibitory potential against insulin amyloidosis. Our investigation unveils collapsible regions within hIAPP that, upon collapse, facilitates hydrophobic and pi-pi interactions, ultimately leading to aggregation. Intriguingly plumbagin exhibits the ability to bind these specific collapsible regions, thereby impeding the aforementioned interactions that would otherwise drive hIAPP aggregation. We have used atomistic molecular dynamics approach to determine secondary structural changes. MSM shows metastable states forming native like hIAPP structure in presence of PGN. Our in silico results concur with in vitro results. The ThT assay revealed a striking 50% decrease in fluorescence intensity at a 1:1 ratio of hIAPP to Plumbagin. This finding suggests a significant inhibition of amyloid fibril formation by plumbagin, as ThT fluorescence directly correlates with the presence of these fibrils. Further TEM images revealed disappearance of hIAPP fibrils in plumbagin pre-treated hIAPP samples. Also, we have shown that plumbagin disrupts the intermolecular hydrogen bonding in hIAPP fibrils leading to an increase in the average beta strand spacing, thereby causing disaggregation of pre-formed fibrils demonstrating overall disruption of the aggregation machinery of hIAPP. Our work is the first to report a detailed atomistic simulation of 22 μs for hIAPP. Overall, our studies put plumbagin as a potential candidate for both preventive and therapeutic candidate for hIAPP amyloidosis.

Structure of cytotoxic amyloid oligomers generated during disaggregation.

Amyloidosis is characterized by the abnormal accumulation of amyloid proteins. The causative proteins aggregate from monomers to oligomers and fibrils, among which some intermediate oligomers considered as major toxins. Cytotoxic oligomers are generated not only by aggregation but also via fibril disaggregation. However, little is known about the structural characteristics and generation conditions of cytotoxic oligomers produced during disaggregation. Herein, we summarized the structural commonalities of cytotoxic oligomers formed under various disaggregation conditions, including the addition of heat shock proteins or small compounds. In vitro experimental data demonstrated the presence of high-molecular-weight oligomers (protofibrils or protofilaments) that exhibited a fibrous morphology and β-sheet structure. Molecular dynamics simulations indicated that the distorted β-sheet structure contributed to their metastability. The tendency of these cytotoxic oligomers to appear under mild disaggregation conditions, implied formation during the early stages of disaggregation. This review will aid researchers in exploring the characteristics of highly cytotoxic oligomers and developing drugs that target amyloid aggregates.

Disaggregation of amyloid-beta fibrils via natural metabolites using long timescale replica exchange molecular dynamics simulation studies.

Amyloid fibrils are self-assembled fibrous protein aggregates that are associated with several presently incurable diseases such as Alzheimer's. disease that is characterized by the accumulation of amyloid fibrils in the brain, which leads to the formation of plaques and the death of brain cells. Disaggregation of amyloid fibrils is considered a promising approach to cure Alzheimer's disease. The mechanism of amyloid fibril formation is complex and not fully understood, making it difficult to develop drugs that can target the process. Diacetonamine and cystathionine are potential lead compounds to induce disaggregation of amyloid fibrils. In the current research, we have used long timescale molecular simulation studies and replica exchange molecular dynamics (REMD) for 1000 ns (1 μs) to examine the mechanisms by which natural metabolites can disaggregate amyloid-beta fibrils. Molecular docking was carried out using Glide and with prior protein minimization and ligand preparation. We focused on a screening a database of natural metabolites, as potential candidates for disaggregating amyloid fibrils. We used Desmond with OPLS 3e as a force field. MM-GBSA calculations were performed. Blood-brain barrier permeability, SASA, and radius of gyration parameters were calculated.

DNA nanostructures prevent the formation of and convert toxic amyloid proteospecies into cytocompatible and biodegradable spherical complexes

AbstractThe deposition of insoluble proteinaceous aggregates in the form of amyloid fibrils within the extracellular space of tissues is associated with numerous diseases. The development of molecular approaches to arrest amyloid formation and prevent cellular degeneration remains very challenging due to the complexity of the process of protein aggregation, which encompasses an infinite array of conformations and quaternary structures. Polyanionic biopolymers, such as glycosaminoglycans and RNAs, have been shown to modulate the self‐assembly of amyloidogenic polypeptides and to reduce the toxicity induced by the formation of oligomeric and/or pre‐fibrillar proteospecies. This study evaluates the effects of double‐stranded DNA (dsDNA) nanostructures (1D, 2D, and 3D) on amyloid self‐assembly, fibril disaggregation, and the cytotoxicity associated with amyloidogenesis. Using the islet amyloid polypeptide (IAPP) whose pancreatic accumulation is the hallmark of type 2 diabetes, it was observed that dsDNA nanostructures inhibit amyloid formation by inducing the formation of spherical complexes in which the peptide adopts a random coil conformation. Interestingly, the DNA nanostructures showed a persistent ability to disassemble enzymatically and thermodynamically stable amyloid fibrils into nanoscale DNA/IAPP entities that are fully compatible with β‐pancreatic cells and are biodegradable by proteolysis. Notably, dsDNA nanostructures avidly trapped highly toxic soluble oligomeric species in complete cell culture media and converted them into non‐toxic binary complexes. Overall, these results expose the potent modulatory effects of dsDNA on amyloidogenic pathways, and these DNA nanoscaffolds could be used as a source of inspiration for the design of molecules to fight amyloid‐related disorders.

Therapeutic potential of Coumarin-polyphenolic acid hybrids in PD: Inhibition of α-Syn aggregation and disaggregation of preformed fibrils, leading to reduced neuronal inclusion formation

This study focuses on the discovery of new potential drugs for treating PD by targeting the aggregation of α-Syn. A series of hybrids combining Coumarin and phenolic acid were designed and synthesized. Four particularly promising compounds were identified, showing strong inhibitory effects with IC50 values ranging from low micromolar to submicromolar concentrations, as low as 0.63 μM. These compounds exhibited a higher binding affinity to α-Syn residues and effectively hindered the entire aggregation process, maintaining the proteostasis conformation of α-Syn and preventing the formation of β-sheet aggregates. This approach holds significant promise for PD prevention. Additionally, these candidate compounds demonstrated the ability to break down preformed α-Syn oligomers and fibrils, resulting in the formation of smaller aggregates and monomers. Moreover, the candidate compounds showed impressive effectiveness in inhibiting α-Syn aggregation within nerve cells, thereby reducing the likelihood of α-Syn inclusion formation resembling Lewy bodies, which highlights their potential for treating PD.

Evolution of Disease-modifying Therapy for Transthyretin Cardiac Amyloidosis.

Transthyretin cardiac amyloidosis (ATTR-CA) represents an inexorably progressive and fatal cardiomyopathy. Increased understanding of the underlying pathogenesis responsible for the misfolding of transthyretin and the subsequent accumulation of amyloid fibrils within the myocardium has led to the development of several disease-modifying therapies that act on different stages of the disease pathway. Tafamidis is the first, and to date remains the only, therapy approved for the treatment of ATTR-CA, which, alongside acoramidis, stabilizes the transthyretin tetramer, preventing disaggregation, misfolding and formation of amyloid fibrils. Gene-silencing agents, such as patisiran, vutrisian and eplontersen, and novel gene-editing therapies, such as NTLA-2001, act to reduce the hepatic synthesis of transthyretin. Anti-amyloid therapies represent another strategy in the treatment of ATTR-CA and are designed to bind amyloid fibril epitopes and stimulate macrophage-mediated removal of amyloid fibrils from the myocardium. Many of these treatments are at an early investigational stage but represent an important area of unmet clinical need and could potentially reverse disease and restore cardiac functions even in patients with advanced disease.

Detection and disaggregation of amyloid fibrils by luminescent amphiphilic platinum(II) complexes.

Cyclometallated Pt(II) complexes possessing hydrophobic 2-phenylpyridine (ppy) ligands and hydrophilic acetonylacetone (acac) ligands have been investigated for their ability to detect amyloid fibrils via luminescence response. Using hen egg-white lysozyme (HEWL) as a model amyloid protein, Pt(II) complexes featuring benzanilide-substituted ppy ligands and ethylene glycol-functionalized acac ligands demonstrated enhanced luminescence in the presence of HEWL fibrils, whereas Pt(II) complexes lacking complementary hydrophobic/hydrophilic ligand sets displayed little to no emission enhancement. An amphiphilic Pt(II) complex incorporating a bis(ethylene glycol)-derivatized acac ligand was additionally found to trigger restructuring of HEWL fibrils into smaller spherical aggregates. Amphiphilic Pt(II) complexes were generally non-toxic to SH-SY5Y neuroblastoma cells, and several complexes also exhibited enhanced luminescence in the presence of Aβ42 fibrils associated with Alzheimer's disease. This study demonstrates that easily prepared and robust (ppy)PtII(acac) complexes show promising reactivity toward amyloid fibrils and represent attractive molecular scaffolds for design of small-molecule probes targeting amyloid assemblies.

Five similar anthocyanidin molecules display distinct disruptive effects and mechanisms of action on Aβ1–42 protofibril: A molecular dynamic simulation study

Alzheimer's disease (AD) is associated with the deposition of amyloid-β (Aβ) fibrillary aggregates. Disaggregation of Aβ fibrils is considered as one of the promising AD treatments. Recent experimental studies showed that anthocyanidins, one type of flavonoids abundant in fruits/vegetables, can disaggregate Aβ fibrillary aggregates. However, their relative disruptive capacities and underlying mechanisms are largely unknown. Herein, we investigated the detailed interactions between five most common anthocyanidins (cyanidin, aurantinidin, peonidin, delphinidin, and pelargonidin) and Aβ protofibril (an intermediate of Aβ fibrillization) by performing microsecond molecular dynamic simulations. We found that all five anthocyanidins can destroy F4-L34-V36 hydrophobic core and K28-A42 salt bridge, leading to Aβ protofibril destabilization. Aurantinidin exhibits the strongest damage to Aβ protofibril (with the most severe disruption on K28-A42 salt bridges), followed by cyanidin (with the most destructive effect on F4-L34-V36 core). Detailed analyses reveal that the protofibril-destruction capacities of anthocyanidins are subtly modulated by the interplay of anthocyanidin-protofibril hydrogen bonding, hydrophobic, aromatic stacking interactions, which are dictated by the number or location of hydroxyl/methyl groups of anthocyanidins. These findings provide important mechanistic insights into Aβ protofibril disaggregation by anthocyanidins, and suggest that aurantinidin/cyanidin may serve as promising starting-points for the development of new drug candidates against AD.

Widely Applicable Strategies Against Cancer, Type II Diabetes, and Neurodegenerative Diseases by Means of Rationally Designed Anti-Amyloidogenic Molecules

An increasing number of amyloidogenic proteins are being recognized for their contribution to the progression of various diseases, including cancer, type II diabetes, and neurodegenerative diseases. Detailed analyses of amyloids using cryo-electron microscopy have led to the development of rationally designed inhibitors of amyloid protein aggregation. In this review, we focused on widely applicable strategies against multiple amyloidogenic proteins based on the use of engineered molecules, namely peptidomimetic foldamers, steric zipper inhibitory peptides, di-phenyl-pyrazole derivatives, and chemicals involved in the disaggregation of amyloid fibrils. These strategies could facilitate efficient drug design across disease categories.

Synthesis, characterization, molecular docking studies, and in vitro elucidation of protein aggregation inhibition potential of 3β-acetoxy steroidal pyrazolines

Protein misfolding and amyloid fibril deposition may lead to several neurodegenerative disorders like Alzheimer's, Parkinson's, Huntington's, and similar amyloid polyneuropathies. Inhibition of fibril formation and disaggregation of mature fibrils by some chemical compounds could be a therapeutic approach toward such chronic diseases. In this study, we synthesized a series of novel steroidal pyrazolines and tested the effects of the series on the in vitro inhibition of human lysozyme aggregation. The effect of synthesized steroidal compounds on the kinetics of protein aggregation inhibition was elucidated by Tryptophan (Trp), 8-anilino-1-naphthalenesulfonic acid (ANS), and Congo red (CR) spectral analysis. Further, we examined that the ring closure reaction in the later step produced a mixture of two steroidal pyrazoline epimers that could only be separated in their acetylated form. The (5’S)-3β-acetoxy steroidal pyrazolines (5a-i) were found as the major product and their structures were examined using NMR techniques. The efficacy of various acid catalysts to catalyze the condensation reaction was also evaluated to obtain better yield in lesser time. In addition, molecular docking studies were also performed to understand the receptor-ligand binding interactions.

Vitamin E modified polyamidoamine dendrimer for piperine delivery to alleviate Aβ1–42 induced neurotoxicity in Balb/c mice model

In Alzheimer’s disease (AD), amyloid beta (Aβ1-42) aggregate formation and neurofibrillary tangles are major pathological hallmarks which are related to neurodegeneration in the brain. To alleviate Aβ1-42 fibrils toxicity vitamin E derivative tocopheryl polyethylene glycol succinate (TPGS) was conjugated with polyamidoamine (PAMAM) dendrimer through carbodiimide reaction to synthesize TPGS-PAMAM. This TPGS-PAMAM was employed to entrap neuroprotective agent piperine (PIP) through an anti-solvent technique to prepare PIP-TPGS-PAMAM. The dendrimer conjugate was prepared to reduce Aβ1-42 induced neurotoxicity and increase acetylcholine levels in AD mice models. The synthesis of dendrimer conjugate was characterized through proton nuclear magnetic resonance (NMR) and Trinitrobenzene sulphonic acid assay (TNBS). Physical characterization of dendrimers conjugates were done through various spectroscopic, thermal and microscopy based techniques. PIP-TPGS-PAMAM showed 43.25 nm particle size with PIP percentage encapsulation efficiency of 80.35%. Further Aβ1-42 fibril disaggregation effect of nanocarrier was evaluated using Thioflavin–T (ThT) assay and circular dichroism (CD). The neuroprotection studies for PIP-TPGS-PAMAM was evaluated against neurotoxicity induced using Aβ1–42 intracerebroventricular (ICV) injected in Balb/c mice. The group of mice administered with PIP-TPGS-PAMAM exhibited an increase in the proportion of random alternations in T-maze test and novel object recognition test (NORT) exhibited an increase in working memory cognitive functions. The biochemical and histopathological analysis revealed PIP-TPGS-PAMAM treated groups enhanced acetylcholine levels, reduced ROS and Aβ1-42 content significantly. Our findings imply that PIP-TPGS-PAMAM enhanced memory and reduced cognitive deficit in mice brain induced by Aβ1-42 toxicity.

Imine-Linked Covalent Organic Framework Modulates Oxidative Stress in Alzheimer’s Disease

Oxidative stress due to Cu2+-triggered aggregation of β-amyloid protein (Aβ) and reactive oxygen species (ROS) overexpression in the brain is an important hallmark of early stages of Alzheimer's disease (AD) pathogenesis. The ideal modulator for improving the oxidative stress microenvironment in AD brains should take both Cu2+ and ROS into consideration, which has been rarely reported. Here, a combined therapeutic strategy was achieved by co-encapsulating superoxide dismutase (SOD) and catalase (CAT) in imine-linked covalent organic frameworks (COFs), which were modified with peptide KLVFF (T5). The nanocomposite SC@COF-T5 exhibited an oxidative stress eradicating ability through ROS elimination and Cu2+ chelation, combined with the inhibition of Aβ42 monomer aggregation and disaggregation of Aβ42 fibrils. In vivo experiments indicated that SC@COF-T5 with a high blood-brain barrier (BBB) penetration efficiency was effective to reduce Aβ deposition, expression of pro-inflammatory cytokines, ROS levels, and neurologic damage in AD model mice, consequently rescuing memory deficits of AD mice. This work not only confirms the feasibility and merits of the therapeutic strategy regarding multiple targets for treatment of early AD pathogenesis but also opens up a novel direction for imine-linked COFs in biomedical applications.