Aβ-40 Y10F Increases βfibrils Formation but Attenuates the Neurotoxicity of Amyloid-β Peptide

Alzheimer’s disease (AD) is characterized by the abnormal aggregation of amyloid-β peptide (Aβ) in extracellular deposits known as senile plaques. The tyrosine residue (Tyr-10) is believed to be important in Aβ-induced neurotoxicity due to the formation of tyrosyl radicals. To reduce the likelihood of cross-linking, here we designed an Aβ-40 analogue (Aβ-40 Y10F) in which the tyrosine residue was substituted by a structurally similar residue, phenylalanine. The aggregation rate was determined by the Thioflavin T (ThT) assay, in which Aβ-40 Y10F populated an ensemble of folded conformations much quicker and stronger than the wild type Aβ. Biophysical tests subsequently confirmed the results of the ThT assay, suggesting the measured increase of β-aggregation may arise predominantly from enhancement of hydrophobicity upon substitution and thus the propensity of intrinsic β-sheet formation. Nevertheless, Aβ-40 Y10F exhibited remarkably decreased neurotoxicity compared to Aβ-40 which could be partly due to the reduced generation of hydrogen peroxide. These findings may lead to further understanding of the structural perturbation of Aβ to its fibrillation

Chitosan Oligosaccharides Inhibit/Disaggregate Fibrils and Attenuate Amyloid β-Mediated Neurotoxicity

Alzheimer’s disease (AD) is characterized by a large number of amyloid-β (Aβ) deposits in the brain. Therefore, inhibiting Aβ aggregation or destabilizing preformed aggregates could be a promising therapeutic target for halting/slowing the progression of AD. Chitosan oligosaccharides (COS) have previously been reported to exhibit antioxidant and neuroprotective effects. Recent study shows that COS could markedly decrease oligomeric Aβ-induced neurotoxicity and oxidative stress in rat hippocampal neurons. However, the potential mechanism that COS reduce Aβ-mediated neurotoxicity remains unclear. In the present study, our findings from circular dichroism spectroscopy, transmission electron microscope and thioflavin T fluorescence assay suggested that COS act as an inhibitor of Aβ aggregation and this effect shows dose-dependency. Moreover, data from thioflavin T assay indicated that COS could significantly inhibit fibrils formation and disrupt preformed fibrils in a dose-dependent manner. Furthermore, the addition of COS attenuated Aβ1-42-induced neurotoxicity in rat cortical neurons. Taken together, our results demonstrated for the first time that COS could inhibit Aβ1-42 fibrils formation and disaggregate preformed fibrils, suggesting that COS may have anti-Aβ fibrillogenesis and fibril-destabilizing properties. These findings highlight the potential role of COS as novel therapeutic agents for the prevention and treatment of AD

Genetic analysis of dTSPO, an outer mitochondrial membrane protein, reveals its functions in apoptosis, longevity, and Ab42-induced neurodegeneration

The outer mitochondrial membrane (OMM) protein, the translocator protein 18 kDa (TSPO), formerly named the peripheral benzodiazepine receptor (PBR), has been proposed to participate in the pathogenesis of neurodegenerative diseases. To clarify the TSPO function, we identified the Drosophila homolog, CG2789/dTSPO, and studied the effects of its inactivation by P-element insertion, RNAi knockdown, and inhibition by ligands (PK11195, Ro5-4864). Inhibition of dTSPO inhibited wing disk apoptosis in response to γ-irradiation or H2O2 exposure, as well as extended male fly lifespan and inhibited Aβ42-induced neurodegeneration in association with decreased caspase activation. Therefore, dTSPO is an essential mediator of apoptosis in Drosophila and plays a central role in controlling longevity and neurodegenerative disease, making it a promising drug targe

Phospholipid-Tailored Titanium Carbide Nanosheets as a Novel Fluorescent Nanoprobe for Activity Assay and Imaging of Phospholipase D

As one of the emerging inorganic graphene analogues, two-dimensional titanium carbide (Ti₃C₂) nanosheets have attracted extensive attention in recent years because of their remarkable structural and electronic properties. Herein, a sensitive and selective nanoprobe to fluorescently probe phospholipase D activity was developed on the basis of an ultrathin Ti₃C₂ nanosheets-mediated fluorescence quenching effect. Ultrathin Ti₃C₂ nanosheets with ∼1.3 nm in thickness were synthesized from bulk Ti₃AlC₂ powder by a two-step exfoliation procedure and further modified by a natural phospholipid that is doped with rhodamine B-labeled phospholipid (RhB-PL-Ti₃C₂). The close proximity between RhB and Ti₃C₂ leads to efficient fluorescence quenching (>95%) of RhB by energy transfer. Phospholipase D-catalyzed lipolysis of the phosphodiester bond in RhB-PL results in RhB moving away from the surface of Ti₃C₂ nanosheets and subsequent fluorescence recovery of RhB, providing a fluorescent “switch-on” assay for the phospholipase D activity. The proposed nanoprobe was successfully applied to quantitatively determine phospholipase D activity with a low limit of detection (0.10 U L^–1) and to measure its inhibition. Moreover, in situ monitoring and imaging the activity of phospholipase D in living cells were achieved using this biocompatible nanoprobe. These results reveal that Ti₃C₂ nanosheets-based probes exhibit great potential in fluorometric assay and clinical diagnostic applications