Neuroprotective effects of verbascoside against Alzheimer’s disease via the relief of endoplasmic reticulum stress in Aβ-exposed U251 cells and APP/PS1 mice

Abstract

Background Endoplasmic reticulum (ER) stress is involved in the progression of Alzheimer’s disease (AD). Verbascoside (VB), an active phenylethanoid glycoside that was first isolated from Verbascum sinuatum (the wavyleaf mullein), possesses anti-inflammatory, antioxidative, and anti-apoptotic effects. The purpose of this study was to elucidate the beneficial effects of VB in amyloid β (Aβ)1–42-damaged human glioma (U251) cells and in APPswe/PSEN1dE9 transgenic (APP/PS1) mice. Methods U251 cells were co-incubated with 10 μM of Aβ1-42 and treated with VB. The protective effects of VB were investigated by using 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyl tetrazolium bromide assay, flow cytometry, fluorescence staining, and transmission electron microscopy. APP/PS1 transgenic mice were treated for 6 weeks with VB. Learning and memory were evaluated using a Morris water maze test. Immunohistochemistry, terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling, thioflavin-S staining, and proteomics analysis were performed to study the potential neuroprotective mechanism. Enzyme-linked immunosorbent assays and western blot were performed to analyze altered protein levels of brain lysates in APP/PS1 mice and/or Aβ1-42-damaged U251 cells. Results In Aβ1-42-damaged U251 cells, VB significantly improved cell viability, inhibited apoptosis, reduced calcium accumulation and the intracellular concentrations of reactive oxygen species, and improved the morphology of mitochondria and ER. In APP/PS1 mice, 6-week administration of VB significantly improved memory and cognition. VB inhibited apoptosis, reduced the deposition of Aβ, reduced the formation of neurofibrillary tangles formed by hyperphosphorylated tau protein, and downregulated the expression levels of 4-hydroxynonenal and mesencephalic astrocyte-derived neurotrophic factor in the brains of APP/PS1 mice. Proteomics analysis of mouse hippocampus suggested that the neuroprotective effect of VB may be related to the reduction of ER stress. This was indicated by the fact that VB inhibited the three branches of the unfolded protein response, thereby attenuating ER stress and preventing apoptosis. Conclusions The results confirmed that VB possesses significant neuroprotective effects, which are related to the reduction of ER stress. These findings support the status of VB as a potentially effective treatment for AD and warrant further research.

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Forsythoside A Mitigates Alzheimer's-like Pathology by Inhibiting Ferroptosis-mediated Neuroinflammation via Nrf2/GPX4 Axis Activation

“…During training, the mice were placed in the water to reach the platform within 60 s. After finding the platform, the mice stayed on the platform for 20 s. The mice that did not find the platform within 60 s were manually led to the platform and stayed there for 20 s. After 3 days of training, the navigation test and probe trial were performed under blinded conditions on days 46 and 47, respectively. As reported in our previous study [19], the mice were placed into the cistern from the opposite side of the platform, and the time it took for mice to find the platform and/or the time they passed through the effective area were recorded.…”

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Astragalin Ameliorates Cognitive Dysfunction Through Inhibiting PI3K/Akt-MTOR-Mediated Autophagic Flow in Hippocampal Neurons of APP/PS1 Mice

“…Then the sections were washed by PBST and Goat anti-mouse IgG H&L (Alexa Fluor® 594) (1:800) was added and incubated at 37°C for 1 h. After washing by PBST, the sections were dyed in 0.3% thio avin S solution for 15 min, and then washed in 70%, 50% I and 50% II ethanol solutions for 5 min. Next, 50% glycerol was used for sealing [24]. Sections were observed by a uorescent microscope.…”