Potential Mechanisms of Shu Gan Jie Yu Capsule in the Treatment of Mild to Moderate Depression Based on Systemic Pharmacology and Current Evidence

Background Shu Gan Jie Yu (SGJY) capsule has a good effect on relieving depressive symptoms in China. However, the mechanism of action is still unclear. Therefore, systemic pharmacology and molecular docking approaches were used to clarify its corresponding antidepressant mechanisms. Methods Traditional Chinese Medicine Database and Analysis Platform (TCMSP), the Encyclopedia of Traditional Chinese Medicine (ETCM), and Swiss Target Prediction servers were used to screen and predict the bioactive components of the SGJY capsule and their antidepressive targets. Mild to moderate depression (MMD) related genes were obtained from GeneCards and DisGeNET databases. A network of bioactive components-therapeutic targets of the SGJY capsule was established by STRING 11.5 and Cytoscape 3.9.0 software. Gene function and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were performed by utilizing Database for Annotation, Visualization, and Integrated Discovery (DAVID) platform. Active components were taken to dock with the hypothetical proteins by iGEMDOCK and SwissDock, and the docking details were visually displayed by UCSF Chimera software. Then, the related research literature of the SGJY capsule was reviewed, summarized, sorted, and analyzed, including experimental evidence and clinical experience. Results Seven active components and 45 intersection targets were included in the study. PPI network had genuinely uncovered the potential therapeutic targets, such as AKT1, HSP90AA1, ESR1, EGFR, and PTGS2. KEGG pathway analysis showed that the mechanism of the SGJY capsule on MMD was mainly involved in the PI3K-Akt signaling pathway. Conclusions In this study, we have successfully predicted the biochemically active constituents, potential therapeutic targets, and comprehensively predicted the related drug-gene interaction of the SGJY capsule for treating MMD and provided a basis for subsequent experiments.


Introduction
Depression is one of the most disabling disorders worldwide with poor quality of life. It affects human social function, and imposes a heavy economic burden on individuals, families, communities, and countries. Due to the increasing social pressure and the role of various other factors, mild to moderate depression (MMD), as an early stage of depression, shows a trend of younger age [1]. Currently, selective serotonin reuptake inhibitors (SSRIs) have been widely used in clinical treatment, but their therapeutic effectiveness is only limited at ∼65% [2]. us, more effective drugs with less adverse reactions are expected to be developed in the future. Nowadays, traditional natural herbs are usually used to relieve depression and balance emotions [3].
Systematic review and meta-analysis have provided effective evidence that Shu Gan Jie Yu (SGJY) capsule showed an effective intervention for essential hypertension patients with insomnia, anxiety or depression in recent years. And it is widely used in the treatment of MMD. e SGJY capsule mainly concludes two Chinese herbs, Acanthopanax senticosus (Rupr. & Maxim.) Harms (ASH) and Hypericum perforatum L. (HPL). e antidepressant mechanism of ASH may be mediated via the central monoaminergic neurotransmitter system and cAMP response element-binding (CREB) protein expression.
erefore, administration of ASH may be beneficial for patients with depressive disorders [4]. HPL, widely known as St. John's wort, is commonly used in clinical practice for its antidepressant properties, as well as anxiolytic its properties [5]. In addition, HPL extract is effective in treating MMD and is safer than SSRIs [6]. Although the SGJY capsule has achieved good clinical efficacy in the treatment of MMD, its mechanism of action is still unclear.
With the rapid development of chemoinformatics and bioinformatics, systematic pharmacology, a technology based on computer simulation, has become a developing interdisciplinary. It applies network pharmacology to indicate the molecular mechanisms of Traditional Chinese Medicine (TCM), and has been widely used in screening bioactive components in TCM. In general, systemic pharmacology technology could evaluate the pharmacological effects and reveal the underlying relationship among active components, potential targets, and multiple diseases [7].
In this study, a systemic pharmacology-based strategy combined with molecular docking approach had been employed to predict bioactive components, potential gene targets, and related signal pathways of the SGJY capsule on depression treatment. e flowchart of research approach is shown in Figure 1.
e screening criteria were set as oral bioavailability (OB) greater than or equal to 30% and drug-likeness property (DL) greater than or equal to 0.18 [9]. e molecular structure was reconfirmed by PubChem platform (https://pubchem.ncbi.nlm. nih.gov/) and saved in .mol2 and SMILES format for further study.

Potential Targets Prediction.
Active components were submitted to Swiss Target Prediction platform (https://www. swisstargetprediction.ch/) based on SMILES format with parameter Probability ≥0.6 in prediction results in order to obtain high-quality targets [10]. "Homo sapiens" was used as selected species. After removing duplicate genes, potential targets related with active components of the SGJY capsule were obtained. MMD-related targets were collected individually from the DisGeNET (https://www.disgenet.org/ home/) and GeneCards (https://www.genecards.org/) databases with the keywords "psychotic depression, mental depression, depressive disorder, mild depression, and moderate depression." All the targets were standardized in the UniProt database (https://www.uniprot.org/).

Network Construction and Gene Analysis.
SGJY-related and MMD-related targets were all imported into the Venny 2.1 system (https://bioinfogp.cnb.csic.es/ tools/venny/). e intersection targets were selected as the potential targets for further analysis. A protein-protein interaction (PPI) network was constructed by using the STRING 11.5 platform (https://string-db.org/), "Organism" was set to "Homo sapiens." An interaction with medium confidence (0.4) was collected.
e network was visually displayed by the Cytoscape 3.9.0 software. en GO function and KEGG enrichment analyses were performed with the DAVID platform (https://david.ncifcrf.gov/tools.jsp). e identifier and species were selected as "official_gene_symbol" and "Homo Sapiens," respectively. e enrichment results, including molecular functional (MF), cell component (CC), biological process (BP), and KEGG pathway enrichment, were obtained and visualized by using imageGP platform (https://www.ehbio.com/ImageGP/index.php/Home/Index/ index.html) as the bubble graph with p value <0.05 [11].

Molecular Docking.
Crystal structures of core proteins were obtained from the RCSB Protein Data Bank (PDB, https://www.rcsb.org/) with high resolution and score. Water molecules were removed from the structure. Potential candidate components of the SGJY capsule in .mol2 format were taken as ligands. Molecular docking was mainly completed by iGEMDOCK 2.1 with default parameters. Afterward, the most potential protein with associated active ingredients at the low energy was used to dock on the SwissDock platform (https://www.swissdock.ch/docking/), and the results were visually displayed by the UCSF Chimera 1.15 software.

Literature Collection and Analysis.
Literature search was performed via PubMed database (https://pubmed.ncbi.nlm. nih.gov/) with the term "Shu gan jie yu." All relevant literature were collected, organized, categorized, and divided into experimental evidence and clinical practice.  Figure 2).

PPI Network Construction and Analysis.
Forty-five intersection genes correlated with MMD were analyzed by the STRING database, and PPI network was established ( Figure 3(a)). A total of 45 nodes and 70 edges were embodied with the average node degree 8.53 and p value <0.01. e most-connected targets were AKT1, HSP90AA1, ESR1, EGFR, PTGS2, GSK3B, MMP9, MMP2, IGF1R, KDR, APP, MCL1, PIK3R1, and MAPT with larger degree (degree > 10), as shown in Table 2 and Figure 3(b). e network of herbscomponents-targets was constructed, including 2 herbs, 7 components, and 45 potential targets, in which the blue hexagons correspond to the putative targets and bioactive components are in pink ( Figure 4).

Gene Function and KEGG Pathway Enrichment Analyses.
To further capture the relationships between the terms, the DAVID platform was used to perform gene function and KEGG pathway analyses with p value <0.05. e main biological processes contained signal transduction, negative regulation of apoptotic process, and protein autophosphorylation ( Figure 5(a)     Evidence-Based Complementary and Alternative Medicine mainly involved plasma membrane, cytoplasm, and nucleus ( Figure 5(b)). Protein, ATP, and identical protein binding were the main molecular functions of intersection genes ( Figure 5(c)). e mechanisms of the SGJY capsule in the treatment of MMD included PI3K-Akt, Ras, and estrogen signaling pathways ( Figure 5(d)). Among them, the PI3K-Akt pathway was the most potential signaling pathway.

Molecular
Docking. PPI network construction and gene analysis indicated that the potential targets of the SGJY capsule against MMD were based on their degree. ey were selected to dock with 7 active components (betulinic, cianidanol, (+)-epicatechin, kaempferol, luteolin, quercetin, and sesamin). Fluoxetine, which was a SSRI and widely used in clinical practice, was used as a positive control [12]. e lowest binding energy shows the most stable combination. e value of fitness was used to evaluate the binding level. e total energy was regarded as a predicted pose in the binding site, which included Van Der Waal (VDW), hydrogen bonding (H-bond) and electrostatic energy, so E total � E VDW + E H-bond + E electrostatic . It was interesting to note that most compounds had a better bonding ability to potential targets than fluoxetine, as shown in Figure 6. Moreover, (+)-epicatechin, kaempferol, luteolin, quercetin, and sesamin were all closely bound to protein MMP9, and    Evidence-Based Complementary and Alternative Medicine sesamin had the better bonding mode with the MMP9 protein than fluoxetine based on binding energy (Figure 7).   Evidence-Based Complementary and Alternative Medicine extract significantly increased the cell viability, suppressed the apoptosis of PC12 cells, and up-regulated CREB protein expression. Neuroprotective effect might be one of the acting mechanisms that accounts for the in vivo antidepressant activity of ASH [14]. e induction of HO-1 expression protected cells against glutamate-induced neuronal cell death. ASH extract could regulate HO-1 expression through the p38-CREB pathway and translocation of Nrf2, and played an important role in the generation of antineuroinflammatory and neuroprotective responses [4]. Moreover, it had beneficial effects on depression behaviors and restored both altered c-fos expression and hypothalamic-pituitary-adrenal (HPA) activity which associated with stress, and may be a novel agent for the treatment of stress-related disorders [15].

Literature Collection and
HPL, popularly called St. John's wort, is used as a medicinal plant for MMD, and is more effective than placebo or some antidepressant drugs. Di Pierro, et al. found that multifractionated hypericum extract has better clinical outcomes in subjects with depression without determining an increased risk of toxicity or reduced tolerability [16]. HPL could regulate the genes that control HPA axis function and influence, like conventional antidepressants. us, at least in part, it plays stress-induced effects on neuroplasticity and neurogenesis [17]. For patients with mild to moderate depression, St John's wort has comparable efficacy and safety when compared to SSRIs [18]. Most of HPL extracts have been shown to be significantly more effective than placebo with at least similar efficacy and better tolerability compared to standard antidepressant drugs. It is a safe and effective way to treat MMD over long periods of time with less adverse effects, and seems especially suitable for a relapse prevention [19][20][21].

Clinical Practice of the SGJY Capsule.
e SGJY capsule is widely used in clinical practice and has achieved very good clinical results in MMD. Clinical efficacy and safety of the SGJY capsule in patients with acute myocardial infarction and depression. Significantly lower adverse event rate was observed in the Shu Gan Jie Yu group. e SGJY capsule has a reliable effect and high safety in patients with depression [22]. In addition, it is very effective for treatment of senile depression [23].
e SGJY capsule is also an effective intervention for essential hypertension patients with insomnia, anxiety, and depression [3]. Yao et al. found that the SGJY capsule significantly reduced the depressive symptoms and improved cognitive functions in poststroke depressive patients through alteration of brain dynamics [24].

Discussion
Seven bioactive components of the SGJY capsule, including betulinic, cianidanol, (+)-epicatechin, kaempferol, luteolin, quercetin, and sesamin, had been successfully obtained by systemic pharmacology strategy. Recent studies also confirmed the antidepressant effects of these compounds. Kaempferol and quercetin had been reported to relieve symptoms of depression and exhibited antidepression effects through acting on interleukin-6 (IL6), mitogen-activated protein kinase 1 (MAPK1), signal transducer, and activator of transcription 3 (STAT3) and transcription factor AP-1 (JUN) [25]. Betulinic produced a significant antidepressantlike effect [26]. Cianidanol, also called (+)-catechin, together with kaempferol and quercetin showed potential capacity in depression management [27]. Luteolin could prevent both neuroimmune responses and behavioral abnormalities including major depressive disorder, which was induced by visceral inflammation [28]. Sesamin inhibited chronic unpredictable mild stress (CUMS)-induced mice depressantlike behaviors and anxiety, which retained immobility and prevented stress-induced decrease of 5-HT and NE in the striatum and serum. Moreover, sesamin treatment significantly prevented CUMS-induced neuroinflammation by inhibiting over-activation of microglia and expressions of inflammatory mediators including iNOS, COX-2, TNF-α, and IL-1β in stressed mice hippocampus and cortex [29]. erefore, multiple active components of the SGJY capsule may exert therapeutic effects on MMD.
Signal transduction has been reported to be closely involved in antidepressant treatment. Gene function and KEGG results indicated that the main molecular mechanism of the SGJY capsule in the treatment of MMD was the PI3K-Akt signaling pathway, KDR, CDK6, IGF1R, EGFR, INSR, GSK3B, HSP90AA1, PIK3CG, MCL1, PIK3R1, and AKT1 genes were enriched in it. Quercetin, luteolin, and kaempferol had been confirmed to be effective in the treatment of MMD by in vivo experiments. e potential PI3K-Akt signaling pathway, a classic signaling pathway in cells, closely relates to the biological process of depression [43,48]. It regulates fundamental cellular functions such as transcription, translation, proliferation, growth, and survival. In addition, the SGJY capsule might exert therapeutic effects on MMD via Ras, estrogen, and Rap1 signaling pathways. Homologous Ras-family small GTPases, including Ras, Rap2, and Rap1, played a different role and presented signal diversity and specificity. Ras signals longterm potentiation via endoplasmic reticulum PI3K and lipid raft ERK, whereas Rap2 and Rap1 signal depotentiation and long-term depression via bulk membrane JNK and lysosome p38MAPK, respectively [49].
us, Ras-family small GTPases related signaling pathways, including Ras-Raf-MAPK [50], Ras-ERK-MAPK [51], and Rap1-MKK3/6-p38 MAPK [52], may be involved in explaining the disease etiology, the clinical symptom, and treatment response of stress-induced depression [53]. Increasing evidence had been manifested that the disturbances of estrogen signaling pathway occurred in psychiatric disorders, especially in female depression [54]. Hence, the role of multiple signaling pathways is under consideration. Further study is warranted to reveal the relationship between core targets activated by potential bioactive components of the SGJY capsule and different related signaling pathways.
Due to the limitations of compounds screening and accuracy of target prediction, the results obtained in this study are general [55]. Although there is some evidence, many in vivo and in vitro experiments are still needed for verification. In short, our study portrayed the ground view of the SGJY capsule in the treatment of mild to moderate depression.

Conclusion
In this study, seven bioactive components of the SGJY capsule have been identified by a systemic pharmacologybased strategy and the intersection targets corresponding to these components and their therapeutic mechanism of MMD have been revealed in detail by the PPI network and pathway enrichment analyses. e result of molecular docking showed that sesamin had a better bonding mode with the MMP9 protein than fluoxetine. In general, bioactive components and the main therapeutic mechanism of the SGJY capsule in the treatment of MMD were successfully predicted, which might provide valuable guidance for further pharmacological research of the SGJY capsule on MMD.

Data Availability
e data used to support the findings of this study are available from the corresponding author upon request.

Disclosure
Taiping Li and Tian Qiu are the co-first authors.

Conflicts of Interest
e authors declare that there are no conflicts of interest.

Authors' Contributions
Hong Xiao and Ning Yang carried out conceptualization, review, editing, resources, supervision, and project administration. Tian Qiu and Yanyan Zeng were responsible for methodology, investigation, formal analysis, and data curation. Bing Kang was involved in methodology, formal analysis, and data curation. Taiping Li and Xianglong Tang performed conceptualization, review, editing, methodology, investigation, and writing of the original draft. Tian Qiu and Taiping Li contributed equally to this work.