Novel Phenylethanoid Glycosides Improve Hippocampal Synaptic Plasticity via the cAMP-CREB-BDNF Pathway in APP/PS1 Transgenic Mice

Introduction: Alzheimer's disease (AD) is a major public health concern worldwide, but there are still no drugs available that treat it effectively. Previous studies have shown that phenylethanoid glycosides (PhGs) have pharmacological effects, which include anti-AD properties, but the underlying mechanisms by which they ameliorate AD symptoms remain unknown.Methods: In this study, we used an APP/PS1 AD mouse model to explore the function of and mechanisms underlying Savatiside A (SA) and Torenoside B (TB) in the treatment of AD. SA or TB (100 mg center dot kg-1 center dot d-1) was orally administered to seven-month old APP/PS1 mice for four weeks. Cognitive and memory functions were measured using behavioral experiments (including the Morris water maze test and the Y-maze spontaneous alternation test). Molecular biology experiments (including Western blotting, immunofluorescence, and Enzyme-linked immunosorbent assays) were used to detect any corresponding changes in signaling pathways.Results: The results showed that SA or TB treatment could significantly reduce cognitive impairment in APP/PS1 mice. We also showed that chronic treatment with SA/TB could prevent spine loss, synaptophysin immunoreactivity, and neuronal loss in mice, thereby improving synaptic plasticity and moderating learning and memory deficits. SA/TB administration also promoted the expression of synaptic proteins in APP/PS1 mouse brains and upregulated phosphorylation of proteins in the cAMP/CREB/BDNF pathway that are responsible for synaptic plasticity. Additionally, chronic SA/TB treatment increased the levels of brain-derived neurotrophic growth factor (BDNF) and nerve growth factor (NGF) in the brains of APP/PS1 mice. Both astrocyte and microglia volumes, as well as the generation of amyloid beta, were also decreased in SA/TB-treated APP/PS1 mice compared to control APP/PS1 mice. Conclusion: In summary, SA/TB treatment was associated with activation of the cAMP/CREB/BDNF pathway and increased BDNF and NGF expression, indicating that SA/TB improves cognitive functioning via nerve regeneration. SA/TB is a promising candidate drug for the treatment of AD.