ABSTRACT
As a small molecule flavonoid, astragalin (AST) has anti-inflammatory, anti-cancer, and anti-oxidation effects. However, the impact and molecular mechanism of AST in Alzheimer's disease (AD) are still not clear. This study aims to investigate the neuroprotective effect and mechanism of AST on APP/PS1 mice and Aß25-35-injured HT22 cells. In this study, we found that AST ameliorated cognitive dysfunction, reduced hippocampal neuronal damage and loss, and Aß pathology in APP/PS1 mice. Subsequently, AST activated autophagy and up-regulated the levels of autophagic flux-related protein in APP/PS1 mice and Aß25-35-induced injury in HT22 cells. Interestingly, AST down-regulated the phosphorylation level of PI3K/Akt-mTOR pathway-related proteins, which was reversed by autophagy inhibitors 3-Methyladenine (3-MA) or Bafilomycin A1 (Baf A1). At the same time, consistent with the impacts of Akt inhibitor MK2206 and mTOR inhibitor rapamycin, inhibited levels of autophagy in Aß25-35-injured HT22 cells were activated by the administration of AST. Taken together, these results suggested that AST played key neuroprotective roles on AD via stimulating PI3K/Akt-mTOR pathway-mediated autophagy and autophagic flux. This study revealed a new mechanism of autophagy regulation behind the neuroprotection impact of AST for AD treatment.
ABSTRACT
Amyloid-ß (Aß) plaque deposits in the brain are considered to be one of the main pathological markers of Alzheimer's disease (AD). The sequential proteolytic cleavage of amyloid precursor protein (APP) by the aspartyl proteases ß-site APP-cleaving enzyme 1 (BACE1) and γ-secretase produces Aß. Therefore, BACE1 inhibition is a very attractive target for the treatment of AD. Our previous work identified a DNA aptamer named A1 that can bind to BACE1 with high affinity and specificity and exhibits a distinct inhibitory effect on BACE1 activity in an AD cell model. The purpose of this research was to test the effect of aptamer A1 in Tg6799 mice. Four-month-old Tg6799 mice were randomly divided into two groups and treated with aptamer A1 and ineffective aptamer A1scr, respectively, by intracerebroventricular injection. Subsequent behavioral experiments showed that treatment with the aptamer A1 improved the cognitive abilities of the AD mice. Western blot indicated that BACE1 and soluble amyloid precursor protein ß (sAPPß) expression significantly decreased in the A1-treated mice. Moreover, aptamer A1 reduced the content of Aß42 and the number and density of senile plaques in AD mice. Therefore, our results indicate that aptamer A1 is a novel specific and potent BACE1 inhibitor and is a promising potential target for the treatment of AD.
Subject(s)
Alzheimer Disease/therapy , Amyloid Precursor Protein Secretases/genetics , Amyloid beta-Peptides/genetics , Aspartic Acid Endopeptidases/genetics , Alzheimer Disease/genetics , Alzheimer Disease/pathology , Amyloid Precursor Protein Secretases/antagonists & inhibitors , Amyloid beta-Peptides/pharmacology , Animals , Aptamers, Nucleotide/genetics , Aptamers, Nucleotide/pharmacology , Aspartic Acid Endopeptidases/antagonists & inhibitors , Brain/drug effects , Brain/pathology , Disease Models, Animal , Genetic Therapy/methods , Humans , Infusions, Intraventricular , Mice , Mice, TransgenicABSTRACT
OBJECTIVE: To investigate changes in synaptic and extrasynaptic N-methyl-D-aspartate receptors (NMDAR) during the development of cultured rat hippocampal neurons. METHODS: Synaptic and extrasynaptic NMDAR channel currents were recorded from 1-day-old rat hippocampal neurons cultured for 1 and 2 weeks with patch-clamp technique in whole-cell configuration and outside-out configuration, respectively. RESULTS: The amplitude of NMDAR-mediated miniature excited postsynaptic current (Meps(CNMDA)) decreased in neurons cultured for 2 weeks as compared with that recorded in neurons cultured for 1 week, and the 2-week neurons showed also much lowered sensitivity to selective NR2B blocker ifenprodil. The amplitude and open probability of extrasynaptic NMDAR in the 2-week neurons were significantly higher than those in the 1-week neurons, but the neurons differred little in conduction and reverse potential. Ifenprodil decreased the high conductance and open probability in both neurons, but the effect was more potent in the 2-week ones. CONCLUSIONS: There can be developmental changes in synaptic and extrasynaptic NMDAR channel currents in cultured rat hippocampal neurons, indicating that different NMDAR subtypes are expressed in the synaptic and extrasynaptic regions during the development of the hippocampal neurons. In 1-week neurons, NR2B are predominant both in synaptic and extrasynaptic regions, and at 2 weeks, synaptic NR2B are replaced by NR2A but NR2B still remains the predominant subtypes outside the synapses.
