Figure 6.

Blocking tau-induced GSK-3β acetylation by intracerebroventricular infusion of P1 attenuates the cognitive and synaptic deficits with reduced p-tau in 3xTg-AD mice. (a,b) Peptide 1 (P1) attenuated memory deficits of 3xTg-AD mice shown by the restored recognition index (a) and discrimination index (b) recorded at 24 h after training in novel object recognition test. (n = 9-10 for each group, one-way ANOVA, ***p < 0.001 vs WT, #p < 0.05, ###p < 0.001 vs 3xTg). (c–f) P1 alleviated the spatial learning deficit in 3xTg-AD mice shown by the decreased latency to find platform at days 5 and 6 during learning trial in Morris water maze test (c) (n = 9-10 for each group, Two-way ANOVA, *p < 0.05, **p < 0.01, ***p < 0.001 vs 3xTg, ##p < 0.01 vs 3xTg+P1), and P1 improved spatial memory shown by the increased platform crossings (d) and target quadrant time (e) during the probe trial, and there were no difference in swimming speed within the four groups (f). (n = 9-10 for each group, one-way ANOVA, ***p < 0.001 vs WT, #p < 0.05, ###p < 0.001 vs 3xTg). (g–h) P1 treatment increased levels of GluN2A, GluN2B, GluA2 and Syt in the hippocampus measured by western blotting. (n = 5 for each group, one-way ANOVA, *p < 0.05, **p < 0.01, ***p < 0.001 vs WT, #p < 0.05, ##p <0.01, ###p <0.001 vs WT+P1, $p < 0.05, $$p < p < 0.01, $$$p < 0.001 vs 3xTg). (i,j) P1 increased spine density in CA1 subset of 3xTg-AD mice measured by Golgi staining. (n = 12 neurons from 5 mice for each group, one-way ANOVA, **p < 0.01, ***p < 0.001 vs WT, #p < 0.05, ###p < 0.001 vs WT+P1, $p < 0.05 vs 3xTg, bar = 20 μm). (k–m) P1 attenuated phosphorylation and acetylation of GSK-3β and tau hyperphosphorylation in 3xTg-AD mice measured by Western blotting (k,l) and immunofluorescence (m). (n = 5 each group, one-way ANOVA, *p < 0.05, **p < 0.01, ***p < 0.001 vs WT, #p < 0.05, ###p <0.001 vs WT+P1, $p < 0.05, $$$p < 0.001 vs 3xTg, bar = 50 μm). Data were presented as mean ± SEM.