Anti-depressant effect of Zhi-zi-chi decoction on CUMS mice and elucidation of its signaling pathway.

Abstract Ethnopharmacological relevance Zhi-zi-chi decoction (ZZCD) has been used for treating depression for centuries as an effectively traditional Chinese medicine. Until now, studies on pharmacological research of ZZCD mostly centered in pharmacokinetic and network pharmacology level. Little was known about its pharmacological mechanism of relieving depression. Aim of the study This study was to evaluate the effect of ZZCD on relieving depression via behavioral tests, serum metabolomics and signaling target expression analysis on chronic unpredictable mild stress (CUMS) model mice. Materials and methods In this study, 70 male Balb/c mice were randomly divided into seven groups. The CUMS exposure lasted 7 consecutive weeks. The mice were administrated with ZZCD for the last 3 weeks. Behavioral tests (body weight test, sucrose preference test, tail suspension test, open field test and forced swimming test) were applied and a serum metabolomics method based on UFLC/Q-TOF-MS with multivariate statistical and global metabolic network analysis was performed to identify potential endogenous metabolites and pathways which may be relevant to depression. Finally, the protein expression of PKA, p-CREB, BDNF, TrkB and PSD-95 in mouse hippocampus was determined by western blot to verify the metabolomics deduction. Results The body weight and sucrose preference were significantly reduced while the immobility time, total distances and time in center were visibly increased in the CUMS mice at the 4th week. After 3-week administration, high and medium dosage groups mice showed status improvement compared to the model group. 76 metabolites were identified as potential biomarkers from the metabolomics profiles in C18 and Hilic systems, of which 48 were trending up and 28 were trending down after administration with ZZCD. In addition, 9 significant pathways related to changed biomarkers were conducted, of which five were lipid metabolism pathways, two were amino acid metabolism pathways, one was translation pathway and one was carbohydrate metabolism pathway. The pathways were closely connected by O-phosphoethanolamine, phosphatidylcholine, L-glutamine, L-aspartic acid, L-arginine, L-glutamic acid, L-proline, gamma-aminobutyric acid and oxoglutaric acid. All of the target contents were significantly reduced in the model group compared with those in control group, while fluoxetine and ZZCD treated groups showed corrections after 3-week administration. The results revealed that the anti-depression efficacy of ZZCD might be associated with PKA-CREB-BDNF-TrkB-PSD-95 pathway influenced by metabolic changes, verifying the pathway annotation speculation. Conclusion This study demonstrated that the establishment of CUMS depression model was successful and ZZCD had a positive treatment effect on depressed mice. Metabolomics results revealed the holistic and interconnected metabolic changes of ZZCD in CUMS mice. The metabolic pathway annotation suggested that the anti-depression mechanism of ZZCD might be related to signaling pathway in brain. PKA-CREB-BDNF-TrkB-PSD-95 signaling expression was a verification and complement to the metabolomics results and provided vital evidence for the anti-depression efficacy of ZZCD.