Effect of Apelin-13 on behavioral changes and hippocampal autophagy of mice with posttraumatic stress disorder / 中华行为医学与脑科学杂志

ABSTRACT

Objective:To investigate the effect and the neural mechanisms of Apelin-13 on the behavior changes of posttraumatic stress disorder (PTSD) model mice.Methods:Totally 32 SPF grade male C57BL/6J mice aged 6 weeks were divided into 4 groups randomly ( n=8 in each group): control group, model group, normal saline group and Apelin-13 group.The mice model of PTSD was established by single-prolonged stress (SPS) method. The mice in normal saline group and Apelin-13 group were respectively given lateral ventricular microinjection of 0.9% sodium chloride solution (2 μL) and Apelin-13 (1.5 μg/μL, 2 μL)after PTSD modeling. The behaviors of mice were evaluated by open field test, elevated plus maze test and Morris water maze test.The morphological structure and numerical changes of hippocampal neurons were observed by hematoxylin and eosin (HE) staining.The expression of phosphoinositide 3-kinase(PI3K), phosphorylated-PI3K(p-PI3K), protein kinase B(Akt), phosphorylated-Akt (p-Akt), forkhead box O3a (FoxO3a), phosphorylated-FoxO3a(p-FoxO3a), autophagy-related proteins including microtubule-associated protein 1 light chain 3(LC3) and sequestosome 1(p62) were detected by Western blot. SPSS 26.0 software was used for data analysis.The escape latency data of repeated learning training in Morris water maze was conducted by repetitive measurement ANOVA.The comparison of other data among multiple groups was conducted by one-way ANOVA and further pairwise comparisons were conducted by LSD test and Tamhane test. Result:(1) Open field test results showed statistically significant differences in the central area activity distance and residence time in central area among mice in the four groups ( F=15.37, 9.63, both P<0.05). The central area activity distance ((0.06±0.03) m) and residence time ((2.48±1.02) s) of the mice in model group were lower than those of the control group ((0.19±0.05) m, (15.00±8.91) s)(both P<0.05). And the central area activity distance((0.12±0.04)m)and the residence time((13.56±7.64)s)were higher than those of model group((0.06±0.03)m, (2.48±1.02)s)and normal saline group((0.06±0.02)m, (2.82±1.52)s)(all P<0.05). Elevated plus maze test results showed statistically significant differences in the numbers and time entering open arms among the four groups ( F=10.74, 19.12, both P<0.05). The numbers((4.50±2.51) times) and the time ((26.95±17.48) s) entering the open arm of mice in model group were both lower than those of the control group ((13.75±4.71) times, (103.75±42.43)s) and Apelin-13 group ((10.00±5.18) times, (55.98±19.49) s) (all P<0.05). Morris water maze test results showed that in the 4-day learning and training phase, the time and group interaction of escape latency was not significant among the four groups ( F=1.15, P=0.34), but time main effect and group main effect were significant ( F=131.65, 16.98, both P<0.05). On the 2nd to 4th day, mice in model group showed significantly increased escape latency than mice in control group and Apelin-13 group(both P<0.05). And the numbers crossing original platform and the time in the target quadrant of Apelin-13 group were both higher than those of model group and normal saline group (all P<0.05). (2) HE staining results showed that neurons in the hippocampal CA1 and CA3 area of mice in model group and normal saline group were swollen and arranged loosely.The hippocampal neurons in control group and Apelin-13 group were arranged neatly and densely. (3) Western blot results showed statistically significant differences in the protein expression of p-PI3K, p-Akt, p-FoxO3a, p62 and the ratio of LC3Ⅱ/LC3Ⅰ among the four groups ( F=21.37, 37.35, 20.71, 13.26, 37.65, all P<0.05). The protein expression of p-PI3K, p-Akt, p-FoxO3a and p62 in Apelin-13 group((0.92±0.07), (0.90±0.09), (0.89±0.13), (1.03±0.08)) were higher than those in model group((0.59±0.04), (0.50±0.07), (0.49±0.11), (0.68±0.04)) and normal saline group((0.61±0.06), (0.50±0.08), (0.53±0.11), (0.70±0.05))(all P<0.05), and the ratio of LC3Ⅱ/LC3Ⅰ in Apelin-13 group(0.60±0.06) was lower than those in model group(0.92±0.10) and normal saline group(0.99±0.05) (both P<0.05). Conclusion:Apelin-13 can alleviate the anxiety-like behavior and impaired spatial learning and memory in PTSD model mice. The mechanism may be related to the up-regulation of PI3K/Akt/FoxO3a autophagy pathway.