L-3-n-butylphthalide reduces tau phosphorylation and improves cognitive deficits in AβPP/PS1-Alzheimer's transgenic mice

L-3-n-butylphthalide (L-NBP), an extract from seeds of Apium graveolens Linn (Chinese celery), has been shown to have neuroprotective effects on cerebral ischemic, vascular dementia and amyloid-β (Aβ)-induced animal models by inhibiting oxidative injury, neuronal apoptosis and glial activation, regulating amyloid-β protein precursor (AβPP) processing and reducing Aβ generation. The aim of the present study was to examine the effect of L-NBP on learning and memory in AβPP and presenilin 1 (PS1) double-transgenic AD mouse model (AβPP/PS1) and the mechanisms of L-NBP in reducing Aβ accumulation and tau phosphorylation. Twelve-month old AβPP/PS1 mice were given 15 mg/kg L-NBP by oral gavage for 3 months. L-NBP treatment significantly improved the spatial learning and memory deficits compared to the vehicle-treated AβPP/PS1 mice, whereas L-NBP treatment had no effect on cerebral Aβ plaque deposition and Aβ levels in brain homogenates. However, we found an L-NBP-induced reduction of tau hyperphosphorylation at Ser199, Thr205, Ser396, and Ser404 sites in AβPP/PS1 mice. Additionally, the expressions of cyclin-dependent kinase and glycogen synthase kinase 3β, the most important kinases involved in tau phosphorylation, were markedly decreased by L-NBP treatment. The effects of L-NBP on decreasing tau phosphorylation and kinases activations were further confirmed in neuroblastoma SK-N-SH cells overexpressing wild-type human AβPP695 (SK-N-SH AβPPwt). L-NBP shows promising candidate of multi-target neuronal protective agent for the treatment of Alzheimer's disease.