Gastrodin ameliorates synaptic impairment, reestablishes mitochondrial membrane potential and reduces oxidative stress in N2a/APP cells through the ERK1/2 and GSK-3beta pathways

Alzheimers disease (AD) is featured by abnormal {beta}-amyloid (A{beta}) deposition, neurofibrillary tangle formation, downstream mitochondrial dysfunction, oxidative stress, and synaptic loss. Gastrodin, a phenolic glycoside, has shown neuroprotective effect and used in the treatment of a range of brain diseases. Here we aim to assess the mechanisms and signaling pathways involved in the neuroprotective effect of gastrodin in murine neuroblastoma N2a cells expressing human Swedish mutant amyloid precursor protein (N2a/APP). The levels of pre- and postsynaptic proteins, amyloid precursor protein C-terminal fragments (APP-CTFs), levels of tau, glycogen synthase kinase-3 {beta} (GSK-3{beta}), extracellular regulated kinase (ERK), and c-Jun N-terminal Kinase (JNK) were assessed by Western blotting. Flow cytometry assays for mitochondrial membrane potential (JC1) and reactive oxidative stress, as well as immunofluorescence staining for lipid peroxidation (4{square}hydroxynonenal) and DNA oxidation (8{square}hydroxy{square}2{square}deoxyguanosine), were performed. We found that gastrodin treatment increased the levels of presynaptic SNAP25, synaptophysin, and postsynaptic PSD95, reduced phosphorylated tau protein Ser396, and APP-CTFs in N2a/APP cells. In addition, gastrodin reduced the levels of reactive oxygen species generation, lipid peroxidation, and DNA oxidation, reestablished mitochondrial membrane potential. Upregulated levels of phosphorylated-GSK-3{beta}, reduced levels of phosphorylated-ERK, and phosphorylated-JNK were involved the protective effect of gastrodin. In conclusion, we demonstrated a neuroprotective effect of gastrodin in N2a/APP cell line.