Research on the mechanism of antidepressive effect of Suanzaoren Decoction through TLR4/MyD88/NF-κB pathway and Wnt/β-catenin pathway

Increased inflammatory response and disruption of neuroplasticity are important mechanisms in the hypothesis of the pathogenesis of depression. Thus, these two aspects are conducive to the development of treatments for depression. Suanzaoren Decoction (SZRD) is a classic traditional Chinese medicine compound for the treatment of insomnia, which can clinically relieve depression symptoms, but its antidepressant pharmacological mechanism remains to be elucidated.Based on the hypothesis of inflammation and neuroplasticity in depression, this study aimed to investigate the antidepressant effect of SZRD and its specific molecular mechanism through chronic unpredictable mild stress (CUMS) induced SD rat model and lipopolysaccharide (LPS) induced BV2 cell neuroinflammation model.The body weight and behavioral indexes of CUMS model rats treated with orally or without oral SZRD for 4 weeks were detected. Hematoxylin and eosin staining was used to observe brain pathological damage. Terminal-deoxynucleoitidyl Transferase Mediated Nick End Labeling (TUNEL) staining was used to observe neuronal apoptosis. Immunofluorescence, ELISA kit and Western blotting were used to detect the inflammatory index Iba-1 and inflammatory factors, as well as the important inflammatory pathway TLR4/MyD88/NF-κB. Enzyme linked immunosorbent assay (ELISA) and western blotting were used to detect neuroplasticity indexes proteins-brain-derived neurotrophic factor (BDNF), presynaptic membrane protein-synaptophysin (SYP), and postsynaptic protein- 95(PSD95), and the key pathway Wnt/β-catenin. The possible mechanism of SZRD antidepressant was further explored in LPS-induced BV2 cells.In vivo and in vitro experiments showed that SZRD treatment significantly reversed the depression-like behaviors in rats, decreased the levels of inflammatory factors and increased the expression levels of BDNF, SYP, PSD95 in depression model rats. Furthermore, SZRD treatment inhibited the activation of TLR4/MyD88/NF-κB and Wnt/β-catenin pathways and reduced the massive nuclear translocation of NF-κB and β-catenin. The addition of NF-κB pathway agonists could partially offset the inhibitory effect of SZRD on the Wnt pathway, and the addition of Wnt pathway agonists could also partially offset the inhibitory effect of SZRD on the TLR4 pathway.This study suggestted that SZRD may exert its antidepressant effect by regulating TLR4/MyD88/NF-κB pathway and Wnt/β-catenin pathway in combination.