Depression is a major health problem affecting over 20% of the global population(Geoffroy et al., 2014; Geoffroy et al., 2017; Stubbs et al., 2016; Guichard et al., 2020). “Guipi Decoction” is a well-known formulation which has excellent effect on treating poor memory, fatigue and palpitations. Ziziphi Spinosae Semen, Poria cocos and Longan were selected from the Guipi Decoction to explore the treatment mechanism and treatment effect of depression. A compound formulae composed including Ziziphi Spinosae Semen, Poria cocos. It can nourish the heart and tranquilize the mind (PRC PCO,2020). Longan can nourish blood and essence, and it was selected to investigate its effect on depression and its mechanism of action. In the study, the active constituents and targets of ZPL were identified by network pharmacological method, and correlated them with depression-related targets to construct a network relationship map between drug-ingredient-target-disease. The protein interaction network of the main target was obtained by analyzing 344 intersecting targets. Then, the molecular mechanism of antidepressant effect of ZPL was analyzed by enrichment analysis of GO and KEGG pathways. Finally, the binding stability of the core targets to the active ingredients was determined by molecular docking.
The PPI network diagram was analyzed and the core targets were determined based on three topological parameters, using Cytoscape software (Fig. 4c). These 13 core targets may have a strong connection with depression treatment. Through the metascape platform, the path analysis of multiple targets was carried out to find the relationship between key targets and paths. Therefore, the relevance of ZPL to depression was closely related to the signaling pathways involved in the core targets. The biological functions of ZPL for depression were mainly related to the ligand receptor action of neural activity, synaptic signaling, and inflammatory response. Studies have indicated that in patients with depression, IL-1 β, IL-6, TNF-α and other pro-inflammatory cytokines increased significantly (Dannehl et al., 2014; Zhang et al., 2018). In addition, the injection of TNF-α could induce depression in mice (Katz et al., 1981), thus confirming the involvement of inflammatory cytokines in the depressed state (Vishnu et al., 2021). Therefore, the decrease of inflammatory response also plays an important role in the treatment of depression. In addition, a possible explanation for the pro-inflammatory theory has been proposed for the pathogenesis of various mood disorders (e.g., depression) (Milenkovic et al., 2019; Miller et al., 2016).
Through the study of GO functional and BP enrichment analysis, the gene expression information can be obtained and the protein transport pattern in the biological pathway can be elucidated (Gong et al., 2021). ZPL-depression related pathways were analyzed in detail by GO and KEGG enrichment analysis. For example, PI3K-AKT signaling pathway and MAPK signaling pathway. The PI3K-AKT pathway plays an important role in the regulation of cell proliferation, survival, differentiation and protein translation (Xing et al., 2020). PI3K-AKT plays an important role in the formation and development of depression (Gong et al., 2021). The MAPK pathway is the key pathway of inflammatory cytokine production and can regulate the expression of inflammatory genes at post-transcription level (Zhou et al., 2017). Some studies have shown that neuronal apoptosis plays an important role in the development of depression (Shen et al., 2018). In the pathway enrichment analysis, there were several pathways about neural cell bodies, synaptic conduction, with high enrichment scores (Fig. 5). Hence, ZPL had an inhibitory effect on depression by acting on neurons in multiple ways. As a serine/threonine kinase, AKT1 plays an important role in intracellular signaling pathways. AKT1 is an important intermediate molecule in the PI3K/AKT signaling pathway, which takes part in the metabolism of a variety of intracellular substances and plays an important role in the regulation of a variety of cellular responses, closely related to oxidative stress, apoptosis and protein synthesis (Abeyrathna et al., 2015; Larson- Casey et al., 2016; Singh et al., 2017; Saatloo et al., 2019). A novel mechanism for activating AKT1 phosphorylation to attenuate apoptosis, AKT1 inhibits apoptosis to repair cerebrospinal fluid (Li et al., 2022). Excess TNF can lead to a variety of inflammatory diseases (Atretkhany et al., 2020). TNF-α is an essential inflammatory cytokine that promotes balance in the body by regulating inflammation, cell proliferation, differentiation, survival and death (Chen and Goeddel, 2002; Walczak, 2011). The cytokine IL-6 is an important neuroimmune factor produced mainly by astrocytes in the central nervous system (Lin et al., 2017). Some studies have suggested the use of IL-6 as a confirmatory marker for major depression in the clinical (Khandaker et al., 2014, Roohi et al., 2021). SRC family kinases can be expressed in many cell types, but are particularly abundant in neural tissue. Primarily, they can regulate the ability of various neuronal channel activities (Wang et al., 2004). In the mouse experiments of Komarova et al. TP53 was found to be strongly expressed during mouse brain development and involved in neurodevelopment (Komarova et al., 1997). Patients with stage IV non-small cell lung cancer carrying EGFR mutations have been shown to exhibit elevated pro-inflammatory marker TNF-α, and present the less depression level than those without EGFR mutations (Jacobs et al., 2017). It was shown by immunoblot analysis that MAPK3 may be an important junction and Camk2b-Mapk3 may serve as a new potential pathway affecting synaptic protein expression in hippocampal neurons (Yang et al., 2022). The CTNNB1 gene encodes the intracellular scaffolding protein β-linked protein. The protein is a key regulator of inflammatory cytokine expression and controls the infiltration of immune cells (Katoh, 2018; Li et al., 2019; Sumida et al., 2018; Xia et al., 2021). As a ligand-activated transcription factor, ESR1 influences hundreds of genes, including the regulation of synthesis and metabolism of various neurotransmitters in the brain, and then affects depression (Różycka et al., 2016). Generally, the key targets related to the development of depression make affects through inflammatory responses, while some ones work through the regulation of synaptic expression in neurons. Furthermore, the specific experiments were needed to to confirm the effectiveness of these targets in the future.