褪黑素对小鼠抑郁样行为和BDNF-ERK-CREB信号通路的作用

Effects of melatonin on behavior and BDNF-ERK-CREB signaling path⁃way in depression-like mice

目的:探讨褪黑素(MEL)对慢性束缚应激(CRS)诱导的小鼠抑郁样行为的影响及其机制。方法:将48只SPF级雄性C57BL/6J小鼠随机分成对照组(n=12)和CRS组(n=36),再将CRS组分为CRS+vehicle、CRS+氟西汀(FLX)和CRS+MEL三个亚组(n=12)。CRS组小鼠经14 d的CRS建模后明确抑郁样行为的变化,随后给予14 d的药物干预和CRS后再次检测行为学变化。取脑组织进行尼氏染色、RT-qPCR、Western blot及免疫荧光染色。结果:与对照组相比,CRS组小鼠体重增长显著下降,强迫游泳实验和悬尾实验不动时间显著增加,糖水消耗量显著减少,旷场实验中央停留时间和中央运动距离均显著缩短(P<0.01)。与CRS+vehicle组相比,CRS+FLX组和CRS+MEL组CRS诱导的小鼠抑郁样行为被显著逆转,额叶皮层和海马中脑源性神经营养因子(BDNF)、细胞外信号调节激酶(ERK)和cAMP反应元件结合蛋白(CREB)的mRNA水平,以及BDNF、磷酸化ERK1/2和CREB蛋白水平均显著升高(P<0.01)。尼氏染色结果显示,CRS+vehicle组小鼠神经元排列不规则,尼氏小体数量减少(P<0.01),而CRS+FLX组和CRS+MEL组小鼠神经元状态显著改善(P<0.01)。免疫荧光染色结果显示,与对照组相比,CRS+vehicle组小鼠额叶皮层和海马CA1区的c-Fos阳性细胞数量均显著增加(P<0.01);与CRS+vehicle组相比,CRS+FLX组和CRS+MEL组小鼠额叶皮层和海马CA1区的c-Fos阳性细胞数量均显著减少(P<0.01)。结论:MEL能够显著缓解CRS诱导的小鼠抑郁样行为,其机制可能与激活BDNF-ERK-CREB信号通路有关。

AIM:To investigate the effect of melatonin(MEL)on the depression behavior in mice induced by chronic restraint stress(CRS).METHODS:Forty-eight SPF-grade male C57BL/6J mice were randomly divided into con-trol group(n=12)and CRS group(n=36).The mice in CRS group were further divided into 3 groups(n=12):CRS+vehi-cle group,CRS+fluoxetine(FLX)group,and CRS+MEL group.Mouse depression model was established by the CRS method for 14 d,and then the depression-like behaviors were observed for modeling validation.After 14 d of drug interven-tion combined with CRS,the behaviors were detected again.Nissl staining,RT-qPCR,Western blot and immunofluores-cence staining were performed in mouse brain tissues.RESULTS:Compared with control group,the weight changes of the mice in CRS group were significantly lowered,the immobility time of forced swimming and tail suspension tests was sig-nificantly increased,the consumption rate of sugar water decreased significantly,and the central time and movement dis-tance in open-field test decreased significantly(P<0.01).Compared with CRS+vehicle group,the depression-like behaviors induced by CRS were successfully reversed by the drugs in both CRS+FLX and CRS+MEL groups.Furthermore,com-pared with CRS+vehicle group,the mRNA levels of brain-derived neurotrophic factor(BDNF),extracellular signal-regulated kinase(ERK)and cAMP response element-binding protein(CREB),and the protein levels of BDNF,phosphorylated ERK1/2 and CREB were increased significantly in both CRS+FLX and CRS+MEL groups(P<0.01).The results of Nissl staining showed that the neurons in CRS+vehicle group were irregularly arranged,and the number of Nissl bodies was de-creased(P<0.01).The neuron status and number of Nissl bodies in both CRS+FLX and CRS+MEL groups were signifi-cantly improved(P<0.01).Immunofluorescence staining showed that the number of c-Fos-positive cells in the frontal cor-tex and hippocampal CA1 region of the mice in CRS+vehicle group was significantly larger than that in control group(P<0.01).Conversely,the number of c-Fos-positive cells in CRS+FLX and CRS+MEL groups was significantly smaller than that in CRS+vehicle group(P<0.01).CONCLUSION:Melatonin can significantly alleviate depression-like behavior in-duced by CRS in mice,which may be related to the activation of BDNF-ERK-CREB signaling pathway.