Abstract
BACKGROUND:
As a traditional digestive medicine, stir-fried Raphani Semen (SRS) has been used to treat food retention for thousands of years in China. Modern research has shown that SRS has a good therapeutic effect on functional dyspepsia (FD). However, the active components and mechanism of SRS in the treatment of FD are still unclear.
OBJECTIVE:
The purpose of this study is to elucidate the material basis and mechanism of SRS for treating FD based on UPLC-Q-Exactive Orbitrap MS/MS combined with network pharmacology and molecular docking.
METHODS:
The compounds of SRS water decoction were identified by UPLC-Q-Exactive Orbitrap MS/MS and the potential targets of these compounds were predicted by Swiss Target Prediction. FD-associated targets were collected from disease databases. The overlapped targets of SRS and FD were imported into STRING to construct Protein-Protein Interaction (PPI) network. Then, the Metascape was used to analyze Gene Ontology (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway after introducing overlapped targets. Finally, the active components and core targets were obtained by analyzing the “component-target-pathway” network, and the affinity between them was verified by molecular docking.
RESULTS:
53 components were identified, and 405 targets and 1487 FD-related targets were collected. GO and KEGG analysis of 174 overlapped targets showed that SRS had important effects on hormone levels, serotonin synapses, calcium signaling pathway and cAMP signaling pathway. 7 active components and 15 core targets were screened after analyzing the composite network. Molecular docking results showed that multiple active components had high affinity with most core targets.
CONCLUSION:
SRS can treat FD through a variety of pathways, which provides a direction for the modern application of SRS in FD treatment.
Keywords
Introduction
Functional dyspepsia (FD) is a common digestive system disease. Although the death rate of FD is not high, it seriously affects people’s daily life. Epidemiological survey showed that patients with FD accounted for 80% of patients with dyspepsia [1]. The symptoms of FD mainly include postprandial fullness, early satiety, epigastric pain and epigastric burning [2]. The causes of FD are multifactorial, including psychological comorbidity, gastrointestinal dysfunction, immune dysfunction, gut microbiota disorder, gut-brain axis dysfunction, visceral hyperalgesia and Helicobacter pylori infection [1, 3, 4, 5]. At present, FD is often treated with eradication of Helicobacter pylori, acid suppression therapy and prokinetic agents, but the mechanism of these drugs is single, and the recurrence rate of FD is high [6]. Modern research has shown that traditional Chinese medicine (TCM) positively affects the treatment of FD [7, 8] and has a broad prospect to find active components and develop new drugs from TCM to treat FD.
Raphani Semen (RS) is the seed of Raphanus sativus L., and has been used as a traditional Chinese medicine for more than one thousand years. RS is usually stir-fried to use for promoting digestion and abdominal distension in clinic [9]. Pharmacological studies have shown that stir-fried Raphani Semen (SRS) can treat FD by promoting gastrointestinal motility [10, 11, 12]. The main components of SRS include glucosinolates, sulfur-containing derivatives, flavonoids, alkaloids, small organic acids and derivatives [13]. The current research of SRS mainly focuses on the compounds, but the mechanism and material basis of SRS in the treatment of FD are still unclear. Therefore, it is necessary to illustrate the mechanism and active components of SRS in treating FD by comprehensive and systematic methods.
Network pharmacology is a promising method that combines pharmacology, biology, informatics and topology analysis technology [14], and has the characteristics of multi-target and multi-pathway, which conforms to the holistic theory of TCM. Nevertheless, traditional network pharmacology usually obtains compounds from databases, and these methods cannot determine whether these compounds actually exist in TCM. At present, UPLC-Q-Exactive Orbitrap MS/MS is widely used in the identification of TCM components because of its high sensitivity, selectivity and resolution. Therefore, UPLC-Q-Exactive Orbitrap MS/MS combined with network pharmacology can improve the accuracy of the results [15, 16].
The purpose of this study is to reveal the mechanism and material basis of SRS in treating FD. Firstly, the components of SRS were identified by UPLC-Q-Exactive Orbitrap MS/MS and Xcalibur 3.0. Then, the possible mechanisms and active compounds of SRS in the treatment of FD were analyzed by network pharmacology and molecular docking (Fig. 1).
Flowchart of the study.
Reagents and medicinal materials
SRS was purchased from Bai Wei Tang Chinese Herbal Medicine Drinks Slice Co., Ltd (Jinan, China); distilled water was obtained from Watson’s (Watsons Food and Beverage Co., Ltd.); formic acid and acetonitrile were purchased from Fisher Scientific (Thermo Fisher Scientific, USA); other reagents and chemicals were of analytical grade.
Sample preparation
SRS was ground into fine powder, 5.0 g SRS powder was extracted with 50 mL water for 30 min, and extracted twice. Subsequently, the supernatant was filtered through 0.22
UPLC-Q-Exactive Orbitrap MS/MS measurement
The UPLC-MS/MS data were obtained on UPLC Ultimate 3000 instrument coupled with a Q-Exactive Orbitrap MS spectrometer (Thermo Fisher Scientific, USA). The sample was separated by a HALO-C18 column (2.1 mm
Identification of compounds in the SRS
A database includes chemical names, molecular formulas, accurate molecular mass, chemical structures and relevant fragments was established by searching PubMed (
Acquisition of the targets of the SRS and FD
The structures of the identified components were drawn by ChemBioDraw Ultra 14.0 software, and these structures were introduced into the Swiss Target Prediction (
Construction of the PPI network and acquisition of the core targets
In order to identify the potential targets of SRS in the treatment of FD, the targets of FD and SRS were introduced into bioinformatics (
GO enrichment and KEGG pathway analysis
A comprehensive and systematic biological function annotation was analyzed after importing the overlapped targets into the Metascape database. Cell component (CC), molecular function (MF) and biological process (BP) were obtained by GO enrichment and the possible pathways were obtained by KEGG pathway analysis [27]. The high count indicates more targets in the pathway, the low
Construction of “compounds-targets-pathway-disease” network and screening of the active compounds
To further elucidate the molecular mechanism of SRS in treating FD, targets of SRS and FD, and the KEGG pathways were input into Cytoscape 3.9.1 to establish a “compounds-targets-pathway-disease” network. The nodes in this network represent compounds, targets, disease and pathways, whereas the lines connecting the nodes represent the interaction between the nodes. The components with topological parameters (BC, CC, degree) greater than the median of the three parameters are considered to be active compounds.
Molecular docking
The core targets were selected for molecular docking with the active compounds. The 3D structures of the active components were downloaded from the PubChem website [28] and corrected on the Chem3D Pro 14.0 software to obtain the most stable structures. The structures of the core targets were downloaded from the Protein Data Bank (PDB) website (
TIC of SRS in positive (a) and negative (b) ion mode analyzed by UPLC-Q-Exactive Orbitrap MS/MS.
Identification of compounds in SRS
A total of 53 compounds were identified by matching with the established database, mainly including small organic acids, glucosinolates, isothiocyanates, alkaloids and flavonoids [30, 31, 32, 33, 34, 35]. The total ion chromatograms (TICs) of the SRS are shown in Fig. 2, and the details of the identified components are shown in Table 1.
Identification of compounds in SRS by UPLC-Q-Exactive Orbitrap MS/MS
Identification of compounds in SRS by UPLC-Q-Exactive Orbitrap MS/MS
Possible fragmentation pathways of trans-sinapic acid (a) and sinapoylglucose (b).
Possible fragmentation pathways of glucoraphenin.
The small organic acids and their derivatives in SRS are mainly phenylpropionic acids and benzoic acids, as well as phenylpropanoid glycosides. A total of 24 small organic acids and their derivatives were identified in SRS. Peak 41, retention time (Rt) was 16.82 min, which was used to illustrate the structure analysis of small organic acids. In the negative ion mode, the molecular formula of the quasi-molecular ion peak
Identification of the glucosinolates
Glucosinolates are secondary plant metabolites containing sulfur and nitrogen atoms that widely exist in Brassicaceae family, which have a common core structure composed of
Identification of alkaloids
The representative alkaloid in SRS is sinapine, which is a quaternary ammonium hydroxide and often exists in the form of sinapine thiocyanate. In this paper, the peak 21 in the positive ion mode was identified as sinapine. The molecular ion peak at
Possible fragmentation pathways of sinapine.
Flavonoids are a class of polyphenolic compounds containing two benzene rings and a heterocyclic pyran ring. The two sides of the two benzene rings are connected by a heterocyclic pyran ring to form the C6-C3-C6 basic skeleton [38]. The flavonoids in SRS are mainly flavonoid glycosides. For peak 36 (Rt: 15.73 min), the [M
Possible fragmentation pathways of rutin.
Isothiocyanates are natural plant products obtained by enzymatic hydrolysis of glucosinolates, which have strong anticancer activity. Peak 41 gave [M
Possible fragmentation pathways of sulforaphane.
A total of 405 targets related to 53 components were obtained from the Swiss Target Prediction database and 1487 targets related to FD were obtained from OMIM, Genecards, Drugbank, PLAM-IST and TTD databases. By overlapping the targets of SRS and FD, 174 common targets were obtained, as shown in Fig. 8.
Venn diagram of the targets between SRS and FD.
The PPI network was constructed by inputting 174 overlapping targets into the STRING platform, and a PPI network containing 174 nodes and 687 interaction edges was obtained, as shown in Fig. 9. In this network, the nodes represent target proteins, and the lines between the nodes represent the interaction between proteins. The median value of degree was 12, the median value of BC was 0.0033, and the median value of CSC was 0.3518. Since there were too many targets whose values were greater than these three parameters, we screened again, with a threshold set as BC
PPI network of SRS in the treatment of FD.
Topological parameters of the core targets
Top 10 items of biological process, cellular component, and molecular function.
The overlapped targets were imported into the Metascape, and the GO terms (MF, CC, BP) and KEGG signaling pathways were selected for analysis. A total of 2379 GO terms were analyzed by Go enrichment (
40 KEGG pathways were obtained by KEGG analysis (
Results of KEGG enrichment analysis (top 20)
Results of KEGG enrichment analysis (top 20)
pathway, serotonergic synapse, cGMP-PKG signaling pathway, epithelial cell signaling in Helicobacter pylori infection and bile secretion. The results showed that the active components of SRS could exert the effect in treating FD through multiple signaling pathways, and we visualized the top 20 pathways (Fig. 11) (Table 3).
Point diagram of KEGG pathway.
The active components of SRS, targets and the top 20 KEGG pathways were inputted into Cytoscape 3.9.1 to construct a “Compounds-Targets-Disease-Pathways” network, as shown in Fig. 12. The network has 488 nodes and 1718 interaction lines, where the purple nodes represent the common targets of SRS and FD, the green nodes represent the components of SRS, and the blue represents the pathways. 21 components were screened out after the first screening (BC
Topological parameter values for the core components
Topological parameter values for the core components
“Compounds-Targets-Disease-Pathways” network.
Information about proteins
Molecular docking results of core target proteins and active components
Based on the results of the PPI network, EP300, TP53, SRC, HSP90AA1, AKT1, PIK3CA, STAT3, CTNNB1, EGFR, HRAS, MAPK1, ESR1, RELA, MAPK8 and RXRA were selected as the core targets. The protein structures of the core targets were selected and downloaded from the PDB database (Protein information is shown in Table 5. Molecular docking was performed to verify the binding activity between 15 core compounds and 7 active compounds. The results showed that
Molecular docking mode with good binding energy of some active components and key targets.
FD is a complex digestive system disease with multiple causes [2], and the current treatment strategies for FD are one-sided and the therapeutic efficacy is non-ideal [6]. TCM has received extensive attention due to its multi-component, multi-target and multi-pathway characteristics. As a TCM that has been used for thousands of years, SRS has been shown to promote gastrointestinal motility and treat FD [10, 11], which clearly indicates that SRS may be a potential candidate drug for the treatment of FD. However, the active components and mechanism of SRS in the treatment of FD are still unclear. In this paper, the material basis and mechanism of SRS for treating FD were analyzed based on UPLC-Q-Exactive Orbitrap MS/MS combined with network pharmacology and molecular docking.
According to the traditional application method of TCM, SRS was extracted by water, and 53 components were identified by UPLC-Q-Exactive Orbitrap MS/MS. Based on the results of network pharmacology, we found that SRS may treat FD through multiple components, multiple targets and multiple pathways. Trans-sinapic acid, cis-sinapic acid, cis-ferulic acid, umbelliferone, cinnamoylglycine, caffeic acid and
PPI network analysis showed that SRS might play an important role in treating FD by acting on some targets, including EP300, TP53, MAPK8, SRC, RELA, ESR1, HSP90AA1, AKT1, PIK3CA, STAT3, CTNNB1, RXRA, EGFR, HRAS and MAPK1. EGFR is a receptor for epithelial growth factor cell proliferation and signal transduction [51, 52]. EGF is closely related to the intestinal structure and function of animals, and has the functions of promoting intestinal development, repairing damaged intestinal tissue, affecting the activity of various intestinal enzymes, improving the digestion and absorption of nutrients and inhibiting the colonization of intestinal bacteria [53]. AKT1 is the most important subtype of AKT, and it is also an important regulatory molecule in the PI3K-AKT signaling pathway [54]. In addition to promoting the efficacy of antidepressants [55], AKT1 can also participate in the development, invasion and metastasis of gastric cancer [56]. The activation of the PI3K-AKT pathway is essential to reduce the gastric mucosal cell damage and apoptosis induced by oxidative stress [57]. Akt activates eNOS, resulting in NO production [58], and NO can participate in gastrointestinal motility, visceral blood flow regulation, mucosal protection and inflammatory response [59]. GSK3B is a downstream factor of AKT, which can affect the occurrence of gastric ulcer and depression by regulating proinflammatory cytokines [60, 61]. ESR1 is a nuclear receptor of the steroid hormone receptor family, which can mediate estrogen to achieve its function. Estrogen can significantly inhibit gastric emptying, change gastric motility and rhythm, and inhibit gastric acid secretion [62], and research showed that the level of estrogen was negatively correlated with the degree of FD [63]. RELA transcription factor is a member of the NF-kappa B family of transcription factors and plays an important role in regulating the processes of inflammation, tumor, metabolism and related diseases [64]. STAT3 can participate in the regulation of inflammatory immune response and the secretion of gastrointestinal hormones to enhance gastrointestinal motility [65]. TP53 can induce apoptosis of damaged cells, which has an important effect on maintaining the integrity of gastrointestinal mucosa [66]. In addition, some targets have been shown to play an important role in gastrointestinal cancer, such as HRAS and SRC [27, 28, 67].
GO enrichment showed that in MF, SRS compounds were closely related to protein kinase activity, kinase binding, protein tyrosine kinase activity, heat shock protein binding and protease binding. At CC level, these compounds had a great influence on membrane raft, membrane side, receptor complex and focal local adhesion. The targets in BP were mainly related to hormone response regulation, kinase activity regulation, exogenous stimulation response and hormone level regulation. Studies have shown that some hormones, such as serotonin, motilin, gastrin, cholecystokinin, and vasoactive intestinal peptide, have an important role in the treatment of FD, which can promote gastrointestinal motility and protect gastric mucosa [68, 69, 70, 71]. The GO enrichment results showed that the active compounds of SRS might exert their therapeutic effects on FD by regulating hormone levels, protein tyrosine kinase activity and phosphatase binding.
KEGG analysis showed that SRS can treat FD by regulating cancer pathway, progesterone-mediated oocyte maturation pathway, cAMP signaling pathway, calcium signaling pathway, adherens junction, p53 signaling pathway, steroid hormone biosynthesis, gap junction, NF-kappa B signaling pathway, serotonergic synapse, epithelial cell signaling in Helicobacter pylori infection and bile secretion. NF-kappa B is a nuclear protein factor that plays an important role in inflammation and cell apoptosis [72]. It has shown that the NF-kappa B pathway mediates the innate defense response of gastrointestinal mucosa and plays an important role in maintaining the stability of intestinal mucosa and intestinal microecology [73]. Moreover, the inhibition of the TLR9/NF-kappa B/iNOS signaling pathway also alleviated the inflammatory state of the duodenum and improved the symptoms of FD [74]. Estrogen and serotonin are also closely related to FD. Research has proved that estrogen can regulate gastrointestinal motility and play an important role in the pathogenesis of FD in perimenopausal women. The lower estrogen level will lead to depression and emotional disorder, reduce sympathetic nerve excitation and vagal tone, and then lead to gastrointestinal motility disorder and visceral hypersensitivity [63, 75]. Serotonin is a neurotransmitter widely distributed in the central nervous system and gastrointestinal tract. Studies have shown that serotonin plays an important role in regulating intestinal motility, inhibiting inflammatory response and regulating emotion [76, 77, 78]. Gap junctions can regulate the electrochemical coupling between interstitial cells of Cajal and smooth muscle. Nerval signals from gastrointestinal tract reach smooth muscle through intermuscle interstitial cells of Cajal, and then regulate the movement of gastrointestinal smooth muscle [79].
The KEGG pathway analysis also found that the mechanism of SRS in treating FD may be related to promoting bile secretion. Among the main components of bile, bile acid, bile salt and bicarbonate play an important role in digestion, so SRS may play a role in promoting digestion by promoting bile secretion [5]. Calcium signaling pathway is also an important pathway for SRS treatment of FD. Ca2 + is related to the formation of adhesion junction, which is a key factor in the early repair process of mucosal injury [80]. At the same time, the concentration of Ca2 + is also related to the contractile activity of gastrointestinal smooth muscle cells [81]. Helicobacter pylori is considered to be one of the pathogenic factors of FD, and SRS may achieve the purpose of treating FD by removing Helicobacter pylori. In short, SRS can treat FD by regulating multiple pathways.
Finally, the results of molecular docking showed that trans-sinapic acid, cis-sinapic acid, umbelliferone, cis-ferulic acid, cinnamoylglycine and caffeic acid could form strong affinity with the amino acid residues of the core target, indicating that these compounds may have high pharmacological activity [82]. However, there are still some limitations in this study. First of all, the compounds in this study are based on the identified compounds in SRS, but some compounds have not been found, and whether these compounds play a role in the treatment of FD requires further study. Secondly, both network pharmacology and molecular docking are virtual screening processes, and the results of molecular docking cannot reflect whether the binding between the targets and the components is activation or inhibition. Therefore, it is necessary to verify furtherly the network pharmacology results in subsequent studies, such as combining artificial intelligence and experimental verification to further determine the mechanisms and material basis of drugs [83, 84].
Conclusion
In this study, the mechanisms and material basis of SRS in the treatment of FD were preliminarily explored based on the network pharmacology and UPLC-Q-Exactive Orbitrap MS/MS. A total of 53 components of SRS were identified by UPLC-Q-Exactive Orbitrap MS/MS, and the network pharmacology and molecular docking results showed that SRS has the characteristics of multi-pathways and multi-targets in the treatment of FD. It may play important roles in regulating hormone levels, promoting gastrointestinal motility, protecting intestinal structure, reducing inflammatory response and improving mood by acting on core targets. This study provides scientific basis for the clinical application of SRS in treating FD, and also provides new insights for the further research of SRS.
Footnotes
Acknowledgments
The authors thank the High Level Traditional Chinese Medicine Key Disciplines of the State Administration of Traditional Chinese Medicine and Pharmacy Platform of Experimental Center of Shandong University of Traditional Chinese Medicine for supporting this study.
Conflict of interest
The authors declare no conflict of interest, financial or otherwise.
Funding
This work was supported by the Shandong Provincial Natural Science Foundation, China (No. ZR2020MH373) and National Natural Science Foundation of China (No. 81503252).
