β-amyloid (Aβ)-mediated neuronal apoptosis contributes to the pathogenesis of Alzheimer's disease (AD). This study aimed to investigate whether astragalosides (AST) could inhibit Aβ-induced apoptosis in vivo and in vitro and to explore the underlying mechanisms. Amyloid β-protein fragment 25-35 (Aβ25-35) was administered to cerebral lateral ventricle of rats to make the AD models in vivo. AST was able to attenuate both cortical cell degeneration and memory deficits in the AD rats. AST also inhibited Aβ25-35-induced cytotoxicity (e.g., decreased cell viability); apoptosis (e.g., increased caspase-3 expression, increased DNA fragmentation, and Tau hyperphosphorylation); synaptotoxicity (e.g., increased loss of both a dendritic marker, microtubule-associated protein 2 (MAP-2) and synaptic proteins, synaptophysins); and mitochondrial dysfunction (e.g., increased mitochondrial membrane potential) in cultured primary rat cortical cells. The beneficial effect of AST in reducing Aβ-induced cytotoxicity, apoptosis, and mitochondrial dysfunction in cortical cells were blocked by inhibition of phosphoinositide 3-kinase (PI3K)-dependent protein kinase B (PKB, as known as AKT) activation with LY294002. In addition, inhibition of extracellular protein kinase (ERK) with U0126 shared with the AST the same beneficial effects in reducing Aβ-induced apoptosis. Our data suggest that the cortical PI3K/AKT and MAPK (or ERK) pathways as appealing therapeutic targets in treating AD, and AST may have a positive impact on AD treatment via modulation of both PI3K/AKT and ERK pathways.
Keywords: Amyloid beta (Aβ); Astragalosides; Memory dysfunction; Neuronal degeneration; Synaptotoxicity.