ABSTRACT
ObjectiveTo investigate the antidepressant effect of Sinisan （SNS） by regulating glycogen aynthase kinase-3β （GSK-3β）/tumor necrosis factor alpha-induced protein 3（A20）/CCAAT enhancer binding protein β（C/EBPβ） to inhibit the activation of microglia. MethodA total of 72 male C57/6J mice were randomly divided into the normal group， model group， fluoxetine group （5.0 mg·kg-1）， low-dose Sinisan group （4.9 g·kg-1）， medium-dose Sinisan group （9.8 g·kg-1）， and high-dose Sinisan group （19.6 g·kg-1）， with 12 mice in each group. After one week of adaptive feeding， chronic unpredictable mild stress （CUMS） was performed to establish the depression model. In the fifth week， drug treatment was conducted for four weeks. In the ninth week， behavioral tests were performed， including sucrose preference test （SPT）， open field test （OPT）， elevated plus maze （EPM） test， and forced swimming test （FST）. Western blot was used to detect the expression levels of interleukin-1β （IL-1β）， interleukin-6 （IL-6）， nitric oxide synthase （iNOS）， GSK-3β， A20， and C/EBPβ in the cortex. The expression of M1-polarized ionized calcium-binding adapter molecule 1 （Iba1） and cluster of differentiation 68 （CD68） in microglia was detected by immunofluorescence. ResultAfter eight weeks of CUMS， compared with the normal group， the mice in the model group had a significantly reduced sucrose preference rate （P<0.01）， and the activity in the central area of the OPT was significantly reduced （P<0.01）. The activity in the open arm area of the EPM test was significantly reduced （P<0.05）， and the immobility time of FST was increased （P<0.01）. The expression levels of inflammatory proteins IL-1β， IL-6， and iNOS were increased （P<0.01）， and the fluorescence co-localization index of Iba1 and CD68 was increased （P<0.05）. The protein expression levels of GSK-3β and C/EBPβ were significantly increased （P<0.05， P<0.01）. After four weeks of SNS intervention， compared with the model group， the mice in the SNS group had significantly increased sucrose preference rate （P<0.01）， significantly increased activities in the central area and the open arm area in the OPT and the EPM test （P<0.05）， and significantly reduced immobility time in the FST （P< 0.01）. The protein expression levels of IL-1β， IL-6， and iNOS were significantly decreased （P<0.05）， and the fluorescence co-localization index of Iba1 and CD68 was decreased in the high-dose SNS group （P<0.05）. The protein expression levels of GSK-3β and C/EBPβ in the medium-dose and high-dose SNS groups were significantly decreased （P<0.01）， and that of A20 was significantly increased （P<0.01）. ConclusionThe antidepressant effect of SNS is related to the regulation of GSK-3β/A20/C/EBPβ protein expression and the inhibition of M1-type activation of microglia.