Research Progress of Traditional Chinese Medicine in Treating Irritable Bowel Syndrome Based on Network Pharmacology and Molecular Docking Technology

Xiaojie KANG, Hongbing ZHAO, Yunfei BAI, Menghan FENG, Qiaoling LIU, Guanglong WANG

1. College of Traditional Chinese Medicine, Inner Mongolia Medical University, Hohhot 010000, China; 2. Hohhot Mongolian Traditional Chinese Medicine Hospital, Hohhot 010000, China

Abstract In recent years, using network pharmacology and molecular docking technology to reveal the therapeutic targets of irritable bowel syndrome (IBS) has become a research hotspot. This paper summarizes 31 studies of traditional Chinese medicine for IBS by domestic and foreign scholars, and expounds the action mechanism of single drug, drug pair and compound prescription in the treatment of IBS from the aspects of drug activity, action target, biological process and pathway analysis. It also discusses the shortcomings and prospects of network pharmacology and molecular docking technology in the field of traditional Chinese medicine research, and provides reference for expanding the research ideas of traditional Chinese medicine in treating IBS.

Key words Network pharmacology, Irritable bowel syndrome, Traditional Chinese medicine, Study on drug activity

1 Introduction

Irritable bowel syndrome (IBS) is a functional bowel disease characterized by abdominal pain, fullness or discomfort, accompanied by abnormal fecal characteristics and changes in defecation habits. Through routine clinical examination, organic diseases that can explain these symptoms can not be found yet. IBS is one of the most common gastrointestinal diseases, affecting about 10% of the global population, and the incidence rate in Asian countries is 5%-10%[1-2]. Traditional Chinese medicine believes that IBS mostly falls into the range of "diarrhea", "abdominal distension" and "abdominal pain". The pathogenesis of IBS has not been fully elucidated. At present, the etiology and pathogenesis of IBS are mostly attributed to gastrointestinal motility disorder, infection, brain-intestinal axis regulation disorder, visceral hypersensitivity, intestinal flora imbalance, social psychology,etc.The disease is acute, lingering and refractory, and often accompanied by emotional symptoms such as depression and anxiety, so it seriously affects the quality of work and life of patients.

With the rapid development of system biology, bioinformatics and polypharmacology, network pharmacology is a new branch and cross-discipline of pharmacology based on the theories of polypharmacology, systematic biology, genomics and proteomics, using the techniques of assemblics, high-throughput screening, network visualization and network analysis, to reveal and analyze the multi-level and multi-angle biological network relationship of "drug-gene-target-disease", and to predict the possible mechanism of action of drugs in order to discover the pharmacological efficacy and mechanism of drugs[3]. Molecular docking is a technical method to study the interaction and recognition between small molecule ligands and protein receptors. In order to provide reference for the further study of TCM treatment of IBS, this paper summarized 31 related papers on network pharmacology and molecular docking techniques for prevention and treatment of IBS from three angles (single drug, drug pair and compound prescription).

2 Mechanism of single traditional Chinese medicine in treating IBS

2.1SaposhnikoviadivaricataDu Jiaxueetal.[4]obtained 18 effective components with good pharmacokinetic characteristics by searching the systematic pharmacology database and analysis platform (TCMSP) of traditional Chinese medicine, mainly including coumarins, volatile oils, chromone,etc.Related studies[5]show that coumarin and its derivatives have anti-inflammatory and antibacterial effects, can inhibit the release of inflammatory factors (IL-6,etc.) in the process of inflammation, and have good analgesic effect; there are 60 predicted targets forS.divaricata. According to the number of gene connection nodes constructed by PPI network, the top ten core genes areIL6,AKT1,CASP3,JUN,CCND1,ESR1,PTGS2,RELA,CDKN1AandMAPK14; functional enrichment analysis involves many biological processes such as anti-inflammatory reaction, negative regulation of apoptosis process, response to estradiol, enzyme binding, transcription factor binding, cysteine endopeptidase activity participating in apoptosis process, protein complex binding and other molecular functions, and there are 13 related items of cell composition, involving cytoplasm, nuclear plasm and cytoplasm,etc.; pathway enrichment analysis suggests thatS.divaricatamay involve AGE-RAGE signaling pathway, IL-17 signaling pathway, p53 signaling pathway and endocrine resistance. The potential targets ofS.divaricatain these signaling pathways are NF-κB, IL-6, p38, ER,etc.Therefore, it can be inferred that the mechanism ofS.divaricatain treating IBS is closely related to inflammatory intervention, estrogen intervention and ER in endocrine resistance.

2.2CodonopsispilosulaMeng Jieetal.[6]obtained 17 candidate chemical constituents ofC.pilosulathrough TCMSP search, and screened out 111 targets with the highest docking degree. Through the analysis of compound-target network, it is found that the main compounds for treating IBS are luteolin, stigmasterol, 7-methoxy-2-methylisoflavone, daidzein, pectin A,etc.The key targets are PGR, NR3C2, ADRB2, PTGS2, AKT1, AKT1, IL-2, IL-10 and IL-4,etc.Most of them are related to inflammatory reaction and immune regulation. The pathways ofC.pilosulaintervening in IBS are glucocorticoid receptor regulatory network, TRAIL signaling pathway, glucocorticoid receptor signaling, AP-1 transcription factor network, integrin-linked kinase signaling transduction, PAR1-mediated thrombin signaling transduction, phosphatidylinositol regulatory network, thrombin/protease-activated receptor (PAR) pathway, TNF receptor signaling pathway and phosphatidylinositol pathway. Inflammatory pathways include TRAIL signaling pathway, TNF signaling pathway,etc.TRAIL molecule can participate in the apoptosis of immune system cells, regulate the apoptosis of T cells through signal transduction, and target killing of natural killer cells,etc.[7]. Studies have shown that anti-TNF can be used to treat inflammatory bowel disease[8], so it is predicted that TNF signaling pathway may be the key pathway ofC.pilosulain treating IBS.

2.3Pogostemoncablin(Blanco) Benth.Ren Hengxinetal.[9]used TcmSP, TCM-PTD and TCM Database@Taiwan database to retrieve 30 effective active components ofP.cablin(Blanco) Benth., and predicted that flavonoids were the main active pharmacodynamic groups. The research showed that[10]flavonoids had the effects of resisting pathogenic microorganisms, regulating gastrointestinal function, resisting inflammation and easing pain,etc.Through the active component-target-metabolic pathway network construction, the core target proteins obtained, namely CRHR1, GUCY2C, TSPO, CHRM1 and OPRK1, are all G protein-coupled receptors, which can participate in cell signal transduction, immune system regulation, autonomic nervous system regulation and maintaining internal water balance[11]. The results of GO enrichment analysis showed that the receptor activity, g-protein coupled receptor activity and protein binding in molecular function were significant, the proportion of plasma membrane, and monolithic membrane in cell components was the highest, and the signal transduction in biological process and coupled receptor protein signal pathway ranked first. The key pathways of KEGG enrichment analysis are neuroactive ligand-receptor interaction, calcium signaling pathway, purine metabolism, long-term depression, regulation of cytoskeleton, involving signal transduction, cell nutrition, neuroregulatory physiology and other processes in human body.

3 Mechanism of traditional Chinese medicine in treating IBS

Ding Lingetal.[12]searched TCMSP database for 20 active constituents ofA.macrocephalaKoidz.-P.lactiflora, mainly including 3β-acetoxyatractylodendron, β-sitosterol, kaempferol,etc.There are 73 joint targets, and the core targets are IL6, AKT1 and TNF. Studies have shown that IL6 and TNF are involved in inflammatory processes, and AKT pathway mainly plays a role in promoting cell survival and inhibiting apoptosis[13]; KEGG pathway enrichment analysis involves tumor necrosis factor signaling pathway, interleukin-17 (IL-17) signaling pathway and Toll-like receptor signaling pathway, and the role of advanced glycation end products and its membrane receptor (AGE-RAGE) signaling pathway is the most significant. AGE-RAGE signaling pathway and pro-inflammatory cytokines, adhesion molecules, growth factor secretion and release, eventually cause tissue damage and chronic cell activation, resulting in diarrhea[14]. GO function enrichment analysis involves many biological processes such as response to extracellular stimuli, cell response to drugs and nutrition level, and many molecular functions such as nuclear receptor activity, heme binding and ligand-activated transcription factor activity. It can be seen thatA.macrocephalaKoidz-P.lactifloracan play a role in treating IBS mainly through anti-inflammation, nutritional support and regulating protein activity.

Yan Haidongetal.[15]also screenedA.macrocephalaKoidz-P.lactiflorapairs to obtain 20 active ingredients, corresponding to 89 drug action targets. Through the network analysis of drug pairs-active ingredients-action targets, it was also proved that kaempferol and β-sitosterol might be the main active ingredients to exert drug efficacy. In GO functional enrichment analysis, biological processes mainly involve toxic substances, cell proliferation, blood circulation, organic cyclic compounds, active oxygen metabolism and cell response to nitrogen compounds,etc.; molecular functions mainly involve G protein-coupled amine receptor activity, protein homodimerization activity, heme binding, nuclear receptor activity and ammonium ion binding,etc.; cell components mainly involve membrane rafts, components of presynaptic membrane, cytoplasmic perinuclear region, nuclear envelope, receptor complex and blood particles,etc.15 signaling pathways including AGE-RAGE signaling pathway, calcium signaling pathway, HIF-1 signaling pathway, cancer pathway, estrogen signaling pathway, platinum resistance and cGMP-PKG signaling pathway in diabetic complications were screened by KEGG pathway enrichment analysis. RAGE plays the role of pro-inflammatory mediator in inflammatory reaction. AGEs are important ligands of RAGE, which can activate MG (microglia) directly or by acting on its receptor RAGE, and induce it to release a large number of inflammatory factors IL-1β and TNF-α[16]. Total paeoniflorins can reduce the high sensitivity of viscera, improve the barrier dysfunction of intestinal epithelial cells caused by tryptase, relieve irritable diarrhea and abdominal pain, and have a protective or therapeutic effect on nerve cells through calcium signaling pathway[17]. It is speculated that AGE-RAGE signaling pathway and calcium signaling pathway may be the main ways forA.macrocephalaKoidz-P.lactiflorato have a therapeutic effect on IBS.

4 Mechanism of traditional Chinese medicine compound prescription in treating IBS

4.1 Danggui Shaoyao PowderDanggui Shaoyao Powder was first published inSynopsisofGoldenChamberwritten by Zhang Zhongjing, a medical sage in the Eastern Han Dynasty. It is composed ofA.sinensis,P.lactiflora,A.macrocephalaKoidz,L.wallichii,P.cocosandA.orientalis. He Jinyietal.[18]found that there are 31 effective active ingredients, the core active ingredients are kaempferol, stigmasterol, camptothecin, myricetin,etc., which have anti-inflammatory, antioxidant and tumor prevention effects. They share 57 targets with IBS, and the core targets are IL-6, PTGS2, JUN, CAT, MAPK8,etc., which participate in cell inflammatory reaction, immune response, cell proliferation and apoptosis. Biological processes in GO functional enrichment analysis mainly include drug reaction, positive regulation of nitric oxide biosynthesis process, organ regeneration, hypoxia reaction,etc.; cell components include fossa, plasma membrane, plasma membrane whole, membrane raft, cytoplasm,etc.; molecular functions include enzyme binding, steroid binding, protein homodimer activity, transcription factor binding, drug binding,etc.KEGG pathway enrichment analysis showed that there were 61 pathways acting on IBS, including TNF signaling pathway, calcium signaling pathway, 5-hydroxytryptamine, dopaminergic synaptic signaling pathway,etc.TNF-α can affect gastrointestinal motility, digestion and absorption function of IBS patients, damage intestinal protective mucosa, stimulate visceral hypersensitivity and aggravate clinical symptoms of IBS[19]. Smooth muscle contraction is closely related to the change of intracellular calcium concentration. High concentration of Ca2+will cause smooth muscle contraction, so calcium pathway will affect the tension, motility and pressure of gastrointestinal smooth muscle. In molecular docking verification, kaempferol, stigmasterol and other compounds were docked with IL-6, JUN, CAT and MAPK8. The docking results showed that the binding of active components of Danggui Shaoyao Powder with target protein was stable and of high quality.

4.2 Sini PowderSini Powder comes from Zhang Zhongjing’sTreatiseonFebrileDiseases—DifferentiatingthePulseSyndromeofShaoyinDisease, and is composed ofB.chinense,P.lactiflora,F.AurantiiImmaturusandG.uralensisFisch. Yan Haidongetal.[20]screened 140 kinds of active ingredients, corresponding to 269 disease targets. The main active ingredients are quercetin, sitosterol, kaempferol, praeruptorin D, luteolin,etc.In addition to anti-inflammatory effects, quercetin also has antibacterial, anti-infection, anti-allergic and blood lipid lowering effects. PPI network analysis showed that the key potential therapeutic targets were AKT1, MAPK1, TP53, CASP3, EGFR, TNF, IL-6,etc.The enrichment analysis of KEGG pathway mainly involves IL-17 signaling pathway, Toll-like receptor signaling pathway, cAMP signaling pathway, tumor necrosis factor signaling pathway, PI3K-Akt signaling pathway, MAPK signaling pathway, NF-κB signaling pathway,etc.Most of them are closely related to digestive system diseases, involving inflammatory pathway and visceral hyperalgesia.

Li Jiarongetal.[21]also proved that quercetin, kaempferol and paeoniflorin are its effective components, and predicted that 89 related targets such as IL-6, AKT1 and TNF act on Toll-like receptor signaling pathway, NF-κB signaling pathway, TNF signaling pathway, cytokine-cytokine receptor interaction and other signaling pathways to regulate visceral pain and anti-inflammation.

In addition, Lu Xinetal.[22]also screened Sini Powder and obtained 144 chemical components mainly including quercetin, kaempferol, luteolin, naringenin, paeoniflorin and β-sitosterol. There are 257 corresponding targets, and the key target proteins in PPI network are TP53, AKT1, IL6, TNF,etc.The pathways regulated by KEGG enrichment analysis are also closely related to PI3K-Akt signaling pathway, IL-17 signaling pathway, TNF signaling pathway and cytokine-cytokine receptor interaction. In molecular docking verification, the results show that the main components have good binding performance with key target proteins.

Liang Yiminetal.[23]retrieved 112 active ingredients, 204 action targets and 152 drug-disease intersection targets, mainly involving IL-17 signaling pathway, NF-κB signaling pathway, VEGF signaling pathway, dopaminergic synaptic pathway, serotonin synaptic pathway and calcium signaling pathway.

4.3 Guchang Zhixie PillGuchang Zhixie Pill is composed of six traditional Chinese medicines:P.mume,C.chinensis,R.Zingiberis,R.Aucklandiae,R.Corydalisand poppy shell. Shi Hailongetal.[24]retrieved 96 active compounds, and found that chlorogenic acid, gingerone, jatradicaline, copdainine, 6-gingerol, jatradicaline hydrochloride, dexicuculline, berberine hydrochloride, methylcopdainine and papaverine mainly acted on inflammation and pain targets respectively, and all of them had different anti-inflammatory and analgesic effects on IBS. 39 key targets were found, among which TPH1, TNF-α, IFN-γ, IL-6, MAO-A and IL-10 were screened out. TPH1 is a key rate-limiting enzyme for biosynthesis of 5-HT in gastrointestinal tract. MAO-A can degrade 5-HT and produce 5-hydroxyindoleacetic acid (5-HIAA). TNF-α and IL-6 can effectively enhance inflammatory effect and promote the proliferation of macrophages or lymphocytes, while IL-10 mainly inhibits the release of pro-inflammatory factors and effectively represses the immune response exerted by macrophages and monocytes[25]. 5-hydroxytryptamine is an indole derivative, which participates in gastrointestinal motility, visceral pain sensing and other physiological functions in gastrointestinal mucosa. The target is mapped to 29 KEGG pathways, and the enrichment analysis of KEGG pathway mainly focuses on 5-HT signaling pathway, smooth muscle cell proliferation, opioid receptor signaling pathway, monoamine transmitter transport, vasodilation, lipoxygenase degradation pathway, intracellular biogenic amine metabolism,etc.Among them, 5-HT signaling pathway has the smallestPvalue, so it is inferred that it mainly plays a pharmacodynamic role by regulating 5-HT signal synthesis or transport pathway.

4.4 Shenling Baizhu PowderShenling Baizhu Powder consists of Sijunzi Decoction plus 11 medicines including yam, white lentils,F.Amomi, lotus meat,C.lacryma-jobi,P.grandiflorumand dried tangerine peel. From Prescription of Peaceful Benevolent Dispensary, Meng Mengetal.[26]found that there were 129 compounds and potential core targets included AChE, ALOX5, BCL2, CCND1 and CTNNB1. The pathway with the highest enrichment degree is tumor necrosis factor (TNF) signaling pathway. Molecular docking results confirmed that daidzin 7-O-glucoside (daidzin) had the highest binding degree with TNF protein in TNF signaling pathway.

4.5 Tongxie Yaofang decoctionTongxie Yaofang decoction comes fromDanxiXinfa, which is composed of dried tangerine peel,A.macrocephalaKoidz,S.divaricataandP.lactiflora. Li Bangjieetal.[27]screened 25 main effective components in Tongxie Yaofang decoction, including 7 chemical types (alkenes, coumarins, fatty acids, flavonoids, sterols, lactones and chromones), and obtained 11 core targets and 26 key pathways. Functional analysis of genes involves vasoconstriction, renin secretion, signal pathway and conduction,etc.The enrichment analysis of KEGG pathway involves the signal pathways related to inflammatory response regulation, intestinal sensation and intestinal function regulation, immune response regulation, mental and psychological regulation, intestinal infection and flora disorder, which play a role in improving intestinal motility abnormality and reducing visceral hypersensitivity to synergistically treat IBS.

4.6 Lishi-Kuijie DecoctionLishi-Kuijie Decoction (KJF) is a prescription summed up by Professor Li Huashan for many years. It is composed ofC.pilosula,A.macrocephalaKoidz,P.cocos, white lentils,P.grandiflorum,A.villosum, dried tangerine peel, lotus plumule, yam, licorice,S.baicalensis,P.lobataandC.chinensis. KJF contains 182 effective compounds and 296 drug targets, corresponding to 86 disease-drug intersection targets. The key compounds include quercetin, kaempferol, luteolin, wogonin and stigmasterol, and the core targets are IL6, VEGFA, TNF-α, IL1B and AKT1. Through GO and KEGG enrichment and molecular docking analysis, KJF can alleviate IBS symptoms by regulating inflammatory response, intestinal bacterial infection, endocrine and neurosensitization. Molecular docking results showed that stigmasterol, a key compound contained in KJF, had strong binding ability with AKT1, EGFR, IL10 and VEGFA.

4.7 Weichang’an PillWeichang’an Pill is composed of 10 traditional Chinese medicines:R.Aucklandiae,A.sinensis, sandalwood, musk,M.officinalis, rhubarb,L.wallichii,F.Aurantii, defatted croton seed powder and jujube. Yang Qiuruietal.[29]screened 31 active compounds. According to the target network interaction diagram of active components, the top 5 chemical components were screened by degree value as tangerinin, β-sitosterol, β-carotene, stigmasterol and 6, 7-dimethoxy-2-(2-phenylethyl) chromone. There are 102 predicted targets, which are mainly concentrated in dopaminergic synapses, tumor necrosis factor signaling pathways, 5-hydroxytryptamine synapses and other related signaling pathways.

4.8 Shugan Jianpi PrescriptionWuling Powder comes fromTreatiseonFebrileDiseasesand consists ofP.umbellatus,P.cocos,A.orientalis,A.macrocephalaKoidz and cassia twig. It contains 27 effective components, which are mainly composed of β-sitosterol, 3β-acetoxyatractylosterone, hederagenin,etc.to prevent and cure IBS and 61 targets are predicted. The key proteins in the network analysis of "compound-disease-target" are PTGS2, ICAM-1, HSP90AA1,etc.The main functions of target are immune response, inflammatory reaction,etc.The main enrichment pathways are TNF signaling pathway, serotoninergic synapse, AGE-RAGE signaling pathway,etc., which play their roles in inhibiting inflammation, regulating intestinal function and visceral sensitivity, and improving mental state to intervene in IBS.

4.9 Yigan Fupi PrescriptionYigan Fupi Prescription is a self-made prescription by Xu Jingfan, a master of Chinese medicine. It consists of dried tangerine peel, friedA.macrocephalaKoidz, friedP.lactiflora,C.chinensis,S.divaricata,E.rutaecarpa,F.Mume, and prepared liquorice root. There are 107 effective compounds and 422 predicted targets in this prescription. The key targets are ABCB1, CFTR, SLC6A4, TP53, EGFR, GCG, PRNP, ADRA2A,etc., which involve the regulation of neurotransmitters, hormones and functional changes, as well as the regulation of gastrointestinal motility, absorption, hormone secretion abnormalities and immune disorders. Pathway enrichment mainly focuses on nerve signal-related, endocrine signal-related and immune inflammation-related signal pathways, such as hippocampal signaling, neuroactive ligand receptor interaction, serotonin-containing synapses, cortisol synthesis and secretion, pancreatic secretion, ABC transporter, mitogen-activated protein kinase, nuclear factor-κB, NOD-like receptor, peroxisome proliferator-activated receptor, Wnt signaling, Th17 cell differentiation,etc.

5 Conclusions

The research on prevention and treatment of IBS with traditional Chinese medicine can use the network pharmacology research platform and related technologies to link complex traditional Chinese medicine, compound prescription and syndrome with modern medical strategies. Whether it is about single drug, drug pair or compound, it involves multiple components, multiple targets and signal pathways, and the components are mainly stigmasterol, luteolin, kaempferol, quercetin, sitosterol and paeoniflorin; the most frequent target proteins are AKT1, TP53, TNF, IL-6, EGFR and MAPK; the related pathways are mainly AGE-RAGE signaling pathway, TNF signaling pathway, HIF-1 signaling pathway, calcium ion signaling pathway, 5-HT signaling pathway, Toll-like receptor signaling pathway, IL-17 signaling pathway, cAMP signaling pathway, PI3K/Akt signaling pathway, NF-κB signaling pathway,etc., playing a synergistic role in protecting intestinal mucosa, stimulating visceral hypersensitivity, resisting cancer and regulating immunity, which provides scientific theoretical support for the treatment of IBS with traditional Chinese medicine. Secondly, the selected target-related pathways and inflammatory factors are closely related to the pathogenesis of IBS, which provides ideas and reference for the analysis of drug action mechanism, later experimental research and clinical application. Network pharmacology research is in its infancy, and there are still many challenges: the tools of screening analysis have certain limitations, which have an impact on the research results, and it is urgent to standardize the research methods and the accuracy of the database needs to be studied; the authenticity of the research results still needs to be verified by in vitro and in vivo experiments before it can be used to guide clinical practice; there is a lack of large sample, multicenter clinical research and basic experimental research. It is believed that with the progress of science and technology, the continuous improvement of database, the further discussion of data mining methods and the mutual penetration and integration of various disciplines, more experiments will be made to verify its authenticity, and the network pharmacology and molecular docking will make a greater contribution in the field of traditional Chinese medicine in time.