AENK blocked SET cytoplasmic retention induced by Oxygen-glucose deprivation (OGD), thereby reducing tau phosphorylation and alleviating the loss of synaptic proteins in hippocampal neurons. (A–C) Oxygen-glucose deprivation was induced for 12 hours to mimic brain acidification environment. Western blotting (A) show that aAEP (molecular weight at 36KD) level was significantly increased in OGD group (B) and SET is retained in the cytoplasm(C). (D) Rat primary hippocampal neurons (DIV7) were incubated with AEP inhibitor/AENK 25 μg for 12 hours following OGD and immunofluorescence staining of SET (red) and AEP (green) were evaluated. (E) Primary hippocampal neurons PP2A level and activity were tested. (F–H) Western blotting (F) showed that in the OGD+AENK group the tau levels of AT8 (G), pT231 (H) were significantly reduced compared with the OGD group. (I–K) Synaptic proteins were measured (I): pre-synaptic proteins synapsin (J) and postsynaptic proteins PSD95 (K). n=3. p value significance is calculated from a one-way ANOVA or two-way ANOVA, data represent mean ± SEM. *p < 0.05, **p < 0.01 and ***p < 0.001 vs OGD group.