Tanshinone IIA regulates glycogen synthase kinase-3β-related signaling pathway and ameliorates memory impairment in APP/PS1 transgenic mice

Our previous findings indicated that tanshinone IIA (tan IIA), a natural component extracted from the root and rhizome of danshen, significantly attenuated β-amyloid accumulation, neuroinflammation, and endoplasmic reticulum stress, as well as improved learning and memory deficits in APP/PS1 transgenic mouse model of Alzheimer's disease (AD). However, whether tan IIA can ameliorate tau pathology and the underlying mechanism in APP/PS1 mice remains unclear. In the current study, tan IIA (15 mg/kg and 30 mg/kg) or saline was intraperitoneally administered to the 5-month-old APP/PS1 mice once daily for 4 weeks. The open-field test, novel object recognition test, Y-maze test, and Morris water maze test were performed to assess the cognitive function. Nissl staining, immunohistochemistry, TUNEL, and western blotting were conducted to explore tau hyperphosphorylation, neuronal injury, and phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt)/glycogen synthase kinase-3β (GSK-3β) signaling pathway. The activity of GSK-3β, acetylcholinesterase (AChE), choline acetyltransferase (ChAT), superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px), and the level of malondialdehyde (MDA) were measured using commercial kits. Our results revealed that tan IIA treatment significantly ameliorated behavioral deficits and improved spatial learning and memory ability of APP/PS1 mice. Additionally, tan IIA markedly attenuated tau hyperphosphorylation and prevented neuronal loss and apoptosis in the parietal cortex and hippocampus. Simultaneously, tan IIA reversed cholinergic dysfunction and reduced oxidative stress. Furthermore, tan IIA activated the PI3K/Akt signaling pathway and suppressed GSK-3β. Taken together, the above findings suggested that tan IIA improves cognitive decline and tau pathology may through modulation of PI3K/Akt/GSK-3β signaling pathway.