Fast green FCF inhibits Aβ fibrillogenesis, disintegrates mature fibrils, reduces the cytotoxicity, and attenuates Aβ-induced cognitive impairment in mice

Luteoloside inhibits Aβ1-42 fibrillogenesis, disintegrates preformed fibrils, and alleviates amyloid-induced cytotoxicity

Abnormal aggregation and fibrillogenesis of amyloid-β protein (Aβ) can cause Alzheimer's disease (AD). Thus, the discovery of effective drugs that inhibit Aβ fibrillogenesis in the brain is crucial for the treatment of AD. Luteoloside, as one of the polyphenolic compounds, is found to have a certain therapeutic effect on nervous system diseases. However, it remains unknown whether luteoloside is a potential drug for treating AD by modulating Aβ aggregation pathway. In this study, we performed diverse biophysical and biochemical methods to explore the inhibition of luteoloside on Aβ1-42 which is linked to AD. The results demonstrated that luteoloside efficiently prevented amyloid oligomerization and cross-β-sheet formation, reduced the rate of amyloid growth and the length of amyloid fibrils in a dose-dependent manner. Moreover, luteoloside was able to influence aggregation and conformation of Aβ1-42 during different fiber-forming phases, and it could disintegrate already preformed fibrils of Aβ1-42 and convert them into nontoxic aggregates. Furthermore, luteoloside protected cells from amyloid-induced cytotoxicity and hemolysis, and attenuated the level of reactive oxygen species (ROS). The molecular docking study showed that luteoloside interacted with Aβ1-42 mainly via Conventional Hydrogen Bond, Carbon Hydrogen Bond, Pi-Pi T-shaped, Pi-Alkyl and Pi-Anion, thereby possibly preventing it from forming the aggregates. These observations indicate that luteoloside, a natural anti-oxidant molecule, may be applicable as an effective inhibitor of Aβ, and promote further exploration of the therapeutic strategy against AD.

Hyperoside Prevents Aβ42-Induced Neurotoxicity in PC12 Cells and Caenorhabditis elegans

Traditional Chinese medicines such as hyperoside-rich Acanthopanax senticosus and Crataegus pinnatifida have been confirmed to exhibit anti-oxidative stress properties. Hyperoside, the main ingredient of numerous antioxidant herbs, may have the ability to postpone the onset of neurodegenerative diseases. This study investigates the possible therapeutic mechanism of hyperoside as a natural antioxidant against Alzheimer's disease (AD) in Caenorhabditis elegans and PC12 cells. Specifically, hyperoside reduced reactive oxygen species (ROS) level and Aβ42-induced neurotoxicity in C. elegans worms. Meanwhile, hyperoside reduced ROS production and increased mitochondrial membrane potentialin Aβ42-induced PC12 cells, which possibly due to the increase of antioxidant enzymes activity and the diminution of malondialdehyde levels. Hoechst 33,342 staining and flow cytometry analysis results suggested that hyperoside reverses cell apoptosis. Network pharmacology predicts potentially relevant hyperoside targets and pathways in AD therapy. As anticipated, hyperoside reversed Aβ42-stimulated downregulation of the PI3K/Akt/Nrf2/HO-1. The PI3K inhibitor LY294002 partially abolished the protective capability of hyperoside. The results of molecular docking further indicated that the PI3K/Akt pathways may be involved in the protection of Aβ42-induced PC12 cells by hyperoside treatment. The study provides theoretical information for research and development of hyperoside as an antioxidant dietary supplement.

Fast green FCF prevents postoperative cognitive dysfunction via the downregulation of the P2X4 receptor in mice

Postoperative cognitive dysfunction (POCD) is a decline in cognitive function affecting the mental health of aged patients after surgery. The pathological mechanisms underlying POCD have not yet been clarified. The overexpression of the P2X4 receptor in the central nervous system (CNS) was reported to be associated with the onset of POCD. Fast green FCF (FGF), a widely used food dye, could decrease the expression of the P2X4 receptor in the CNS. This study aimed to explore whether FGF could prevent POCD via the down-regulation of CNS P2X4 receptor. Exploratory laparotomy under the anesthesia of fentanyl and droperidol was carried to establish an animal model of POCD in 10-12-months-olds mice. FGF significantly attenuated cognitive impairments and down-regulated the expression of the P2X4 receptor induced by surgery in mice. Moreover, the blockade of CNS P2X4 receptor by intrahippocampal injection of 5-BDBD induced cognitive-enhancing effects on POCD mice. In addition, the effects of FGF were abolished by ivermectin, which is a positive allosteric modulator of the P2X4 receptor. FGF also inhibited M1 polarization of microglia cells, decreased the phosphorylation of nuclear factor-κB (NF-κB), and reduced the production of pro-inflammatory cytokines. These results suggested that FGF produced anti-POCD cognitive-enhancing effects via down-regulation of the P2X4 receptor-associated neuroinflammation, providing a support that FGF might be a potential treatment for POCD.

Rose Bengal inhibits β-amyloid oligomers-induced tau hyperphosphorylation via acting on Akt and CDK5 kinases

RATIONALE

Tau hyperphosphorylation and aggregation is considered as a main pathological mechanism underlying Alzheimer's disease (AD). Rose Bengal (RB) is a synthetic dye used for disease diagnosis, which was reported to inhibit tau toxicity via inhibiting tau aggregation in Drosophila. However, it was unknown if RB could produce anti-AD effects in rodents.

OBJECTIVES

The research aimed to investigate if and how RB could prevent β-amyloid (Aβ) oligomers-induced tau hyperphosphorylation in rodents.

METHODS AND RESULTS

RB was tested in vitro (0.3-1 μM) and prevented Aβ oligomers-induced tau hyperphosphorylation in PC12 cells. Moreover, RB (10-30 mg/kg, i.p.) effectively attenuated cognitive impairments induced by Aβ oligomers in mice. Western blotting analysis demonstrated that RB significantly increased the expression of pSer473-Akt, pSer9-glycogen synthase kinase-3β (GSK3β) and reduced the expression of cyclin-dependent kinase 5 (CDK5) both in vitro and in vivo. Molecular docking analysis suggested that RB might directly interact with GSK3β and CDK5 by acting on ATP binding sites. Gene Ontology enrichment analysis indicated that RB might act on protein phosphorylation pathways to inhibit tau hyperphosphorylation.

CONCLUSIONS

RB was shown to inhibit tau neurotoxicity at least partially via inhibiting the activity of GSK3β and CDK5, which is a novel neuroprotective mechanism besides the inhibition of tau aggregation. As tau hyperphosphorylation is an important target for AD therapy, this study also provided support for investigating the drug repurposing of RB as an anti-AD drug candidate.

Molecular Insights into the Inhibitory Effect of GV971 Components Derived from Marine Acidic Oligosaccharides against the Conformational Transition of Aβ42 Monomers

GV971 derived from marine acidic oligosaccharides has been used to cure Alzheimer's disease (AD). However, the molecular mechanism of its inhibition of the conformational transition of amyloid β-proteins (Aβ) is still unclear. Herein, molecular dynamics simulations were used to explore the molecular mechanism of the main GV971 components including DiM, TetraM, HexaM, and OctaM to inhibit the conformational conversion of the Aβ42 monomer. It is found that the GV971 components inhibit the conformational transition from α-helix to β-sheet and the hydrophobic collapse of the Aβ42 monomer. In addition, the binding energy analysis implies that both electrostatic and van der Waals interactions are beneficial to the binding of GV971 components to the Aβ42 monomer. Among them, electrostatic interactions occupy the dominant position. Moreover, the GV971 components mainly interact directly with the charged residues D1, R5, K16, and K28 by forming salt bridges and hydrogen bonds, which specifically bind to the N-terminal region of Aβ42.