Effect of icariin on depressive behaviour in rat pups. Evidences for its mechanism of action by integrating network pharmacology, metabolomics and gut microbiota composition.

BACKGROUND: Prenatal stress (PS) can cause cognitive disorder and a range of psychological illnesses, including anxiety and depression. Icariin (ICA) has shown promising effects in improving PS-induced depressive behaviour. However, its mechanism of action remains unclear.

PURPOSE: This study was performed to reveal the key targets, metabolites and gut microbiota for ICA in improving depressive behaviour in PS rat pups.

METHODS: A prenatal restraint stress animal model was established for Sprague-Dawley (SD) rats in late pregnancy. Male pups were randomly divided into six groups: no stress group (NS), PS group, PS + saline group (PS_S), PS + high-dose ICA group (ICAH, 80 mg/kg*day), PS + low-dose ICA group (ICAL, 40 mg/kg*day) and PS + fluoxetine group (FLU, 10 mg/kg*day). The depressive behaviour of each group of rat pups was evaluated using open field test, forced swimming test and sucrose preference test. Different metabolites were identified using untargeted metabolomics of serum and faeces, and metabolic pathways were analyzed through MetaboAnalyst. Targets for ICA acting on depression were determined after network pharmacology was applied. An integrated network of network pharmacology and metabolomics were constructed using Cytoscape software, and molecular docking were performed to verify the interactions between ICA and key targets. Finally, gut microbiota of rat pups in each group were analyzed after 16S rDNA sequencing.

RESULTS: PS could cause rat pups to exhibit depressive behaviour, and ICA could significantly improve this depressive behaviour. A total of 49 differential metabolites were found in serum and 23 differential metabolites were found in faeces, and 24 metabolites in serum and 6 metabolites in faeces could be reversed following ICA administration. Integrated analysis focused on five key targets (i.e. adenosyl homocysteinase; medium-chain specific acyl-CoA dehydrogenase, mitochondrial; thymidine phosphorylase; cGMP-specific 3',5'-cyclic phosphodiesterase and xanthine dehydrogenase/oxidase) and three metabolites (i.e. palmitoylcarnitine, methionine and hypoxanthine). Molecular docking indicated that ICA combined well with key targets. Gut microbiota analysis showed that g_Bacteroides, f_Bacteroidaceae and s_Lactobacillus reuteri were required for ICA to improve depressive behaviour.

CONCLUSION: In this study, the antidepressant mechanism of ICA was clarified with a strategy of integrating metabolomics, network pharmacology and gut microbiota. ICA has a good effect on improving metabolism and increasing the abundance of probiotics in the intestine. The present research provided new insights into the anti-depressant mechanism of ICA.