1. Introduction
The traditional herb
Cirsium japonicum (
Radix Cirsii Japonici) has been widely used for the treatment of hemorrhagic fever, hepatitis, coagulation disorders, and urinary tract disorders [
1,
2,
3,
4,
5]. Several studies have demonstrated that the aqueous extract of
C. japonicum exhibits effective therapeutic potential against infectious jaundice and chronic hepatitis [
6]. Additionally, it displays inhibitory activity against
Mycobacterium tuberculosis,
Neisseria meningitidis,
Mycobacterium diphtheriae,
Staphylococcus aureus,
Mycobacterium typhi,
Mycobacterium paratyphi, and
Mycobacterium anthracis [
7]. Furthermore, it has been found to ameliorate metabolic disorders associated with steatohepatic conditions induced by high-fat diets [
8]. Aqueous, alkaline, and acidic alcoholic extracts of
C. japonicum, as well as aqueous extracts of leaves, demonstrate antihypertensive effects. Clinical reports have also documented the use of root tablets for hypertension treatment. Additionally,
C. japonicum has been reported to enhance immunity, promote lipid metabolism, exhibit diuretic and hepatoprotective properties, enhance ethanol metabolizing enzyme activity, and reduce lipid peroxidation [
9]. However, the main components and potential mechanisms of
C. japonicum remain unclear.
With the rapid development of systems biology, bioinformatics, and pharmacology, network-based drug discovery has emerged as a promising method for developing effective drugs. In 2007, Hopkins et al. introduced the concept of "network pharmacology", which utilizes systematic biology to analyze drug intervention and potential therapeutic targets for diseases [
10,
11,
12,
13,
14,
15]. Network pharmacology emphasizes a shift from the traditional "one target, one drug" strategy to a novel "network target, multi-component" strategy [
16]. In the field of traditional Chinese medicine research, it is widely employed due to its holistic and systematic nature that aligns with the principles of traditional Chinese medicine prescriptions [
17,
18,
19]. Molecular docking is also extensively utilized in material basis research on traditional Chinese medicine as computer-aided drug design method that relies on interactions and affinities between targets and active compounds [
20,
21,
22,
23,
24,
25].
Network pharmacology employs network methods to analyze the intricate interplay among drugs, diseases, and targets, while also investigating the synergistic effects of multiple components on diseases. This approach closely aligns with the theoretical framework of holistic concepts and diagnosis and treatment in Chinese medicine, serving as a contemporary scientific methodology for elucidating the material basis of traditional Chinese medicines’ efficacy and mechanisms of action. It facilitates visualization analysis of compound-target-signaling pathways through multidisciplinary approaches such as systems biology, bioinformatics, and multi-omics linkage. To some extent, this analysis reveals the therapeutic effectiveness of each active ingredient in natural plants [
26,
27,
28,
29]. In recent years, network pharmacology has been widely used to predict the mechanism of action between natural active ingredients and diseases.
The present study employed network pharmacology and molecular docking methods to investigate the underlying network mechanism of the anti-inflammatory effects of active ingredients in C. japonicum, elucidating their synergistic actions through multiple targets and pathways. In addition, the anti-inflammatory effect of vanillin, a potent component of C. japonicum, was also assessed in mouse macrophages.
4. Discussion
C. japonicum, a widely accessible and cost-effective Chinese herbal medicine, possesses various functions such as bacteriostasis, anti-inflammation, blood coagulation and hemostasis, blood pressure reduction, and anti-tumor effects [
32]. However, the precise mechanism underlying its anti-inflammatory action remains unclear. This study employs network pharmacology and molecular docking to investigate the anti-inflammatory effects of
C. japonicum, followed by
in vitro experimental verification at the cellular level.
Flavonoids, widely distributed in
Cirsium, is also the most abundant component and the main active ingredient of
Cirsium. It possesses various biological activities such as anti-oxidation, anti-tumor, anti-inflammation, and liver, cardiovascular, and cerebrovascular protection [
33,
34,
35,
36]. In this study, 14 effective components of
C. japonicum were obtained from the TCMSP website, primarily including methyl linoleate, oleic acid, stigmasterol, and sitosterol. Previous studies have demonstrated that stigmasterol exhibits potent anti-cancer properties, while also showing effects against osteoarthritis and inflammation. Moreover, it displays potent activity against parasites, fungi, and bacteria, while also exhibiting immunomodulatory and neuroprotective effects through its antioxidant properties [
37,
38,
39,
40,
41]. One study conducted by Feng et al. [
42] has revealed that stigmasterol significantly inhibits colon shortening and reduces colitis severity by suppressing pro-inflammatory IL-1β, IL-6, and cyclooxygenase-2 (COX-2) monocyte chemotactic protein release. Additionally, stigmasterol improves intestinal function and regulates fat metabolism to alleviate hepatic steatosis in rats by fortifying the intestinal barrier and enhancing bile acid metabolism [
43]. β-sitosterol, a phytosterol with anti-inflammatory properties, exerts regulatory effects on blood glucose metabolism [
44]. Xiao et al. [
45] demonstrated that β-sitosterol reduces serum TNF-α levels in rats, thereby decelerating the progression of gastric mucosa damage through decreased release and aggregation of inflammatory factors within the gastric mucosa. Moreover, the combination of β-sitosterol and aspirin can enhance the anti-inflammatory efficacy of aspirin [
46].
Based on network pharmacology, we conducted a systemic analysis on the active components, targets, related pathways, and biological processes of
C. japonicum. Through analyzing the relevant database of network pharmacology, a total of 14 active components and their corresponding 171 gene targets were identified for
C. japonicum. The drug-component-target-disease network diagram was constructed to reveal that 14 effective active components in
C. japonicum can synergistically act on 32 anti-inflammatory targets (
Figure 2). The 14 anti-inflammatory components primarily consist of methyl linoleate, oleic acid, β-starch acetate, and sterols (such as stigmasterol sitosterol). Among them, oleic acid can inhibit the LPS-induced inflammatory reaction by down-regulating the expression of the nuclear factor kappa-B (NF-κB) signaling pathway [
47]. Methyl linoleate effectively inhibits the expression of IL-1βin THP-1 cells.
In the PPI network visualization analysis, ADRB2, PTGS2, NOS3, BDNF, and PPARG have been identified as potential core targets for the anti-inflammatory effects of
C. japonicum (
Figure S1). Among them, ADRB2 is a crucial β2-adrenergic receptor involved in maintaining hepatocellular carcinoma cell proliferation and survival. Additionally, it has been found to attenuate osteoarthritis-like defects in temporomandibular joints when conditionally detected in mice [
48,
49]. PTGS2, also known as COX-2 enzyme, plays a significant role in the inflammatory response by catalyzing arachidonic acid conversion to prostate H2, which triggers the inflammatory cascade [
50]. The expression of PTGS2 is regulated by various stress-related factors and serves as an important regulator; up-regulated PTGS2 significantly contributes to inflammation regulation through glucagon production [
51]. Nitric oxide (NO) plays a crucial role in regulating various aspects of vascular function, including smooth muscle cell proliferation and migration, vascular tone, endothelial permeability, and endothelial-leukocyte interactions. It serves as a key anti-atherogenic factor in the endothelium [
52]. Endothelial-type nitric oxide synthase 3 (NOS3), encoded by a gene located on chromosome 7q35-36, is responsible for maintaining vascular homeostasis and regulating endothelial function. NOS3 genetic polymorphisms have been demonstrated to exert an impact on NO levels, lipid profiles, and are associated with hypertension [
53] as well as diabetic foot ulcers [
54]. BDNF represents a crucial class of neurotrophic factors that play an essential role in regulating neuronal proliferation, differentiation, maturation, and pro-neuronal regeneration; it constitutes a fundamental factor in ongoing depression research [
55]. BDNF and its receptor, tyrosine kinase receptor B (TrκB), have been implicated in the pathogenesis of various neurological disorders [
56]. Furthermore, activation of the BDNF/TrκB signaling pathway has shown potential for ameliorating memory deficits in rats with Alzheimer's disease [
57]. PPARG belongs to the nuclear transcription factor superfamily as a subtype of peroxisome proliferator-activated receptor and has been demonstrated to mitigate inflammatory responses by inhibiting the NF-κB signaling pathway, making it a promising therapeutic molecular target for diverse malignant tumors [
58].
In the GO and KEGG pathway analyses of 32 targets related to anti-inflammatory effects of
C. japonicum, it was revealed that the biological processes primarily involved in
C. japonicum include response to LPS, negative regulation of cellular regulatory processes, response to hypoxia, negative regulation of macrophage-derived foam cell differentiation, and response to activity (
Figure 3). The anti-inflammatory activity of
C. japonicum mainly involves signaling pathway processes, such as relaxin signaling pathway, arginine biosynthesis pathway, prostate cancer pathway, AGE-RAGE pathway in diabetic complications, apocynin signaling pathway, and PI3K-Akt signaling pathway (
Figure 4). Among these pathways, the PI3K/Akt signaling pathway is a crucial intracellular mechanism that responds to extracellular signals and regulates various cellular and molecular functions, including metabolism, survival, growth, and angiogenesis. Its involvement in gastritis has also gained significant attention in recent years due to its role in cell growth, proliferation, apoptosis, as well as blood glucose regulation [
59]. Several studies have demonstrated that cytokines such as TNF-α and IL-6 can attenuate inflammatory responses by modulating the PI3K-Akt signaling pathway [
60]. Molecular docking results further confirmed that the ability of active ingredients from
C. japonicum, including sitosterol, vanillin, stigmasterol, etc., to bind key targets (such as BNDF, PPARA, PPARA, etc.) and form hydrogen bonding interactions (
Figure 5). Notably, vanillin exhibited a higher binding affinity than oleic acid with binding energies ranging from -5.54 to -3.35 kal (
Table S1). Moreover, vanillin effectively suppressed the expression of pro-inflammatory factors (such as IL-6 and IL-1β) in mouse macrophages while promoting the expression of anti-inflammatory factor IL-10 (
Figure 6). These findings suggest that
C. japonicum possesses significant preventive and therapeutic potential against LPS-induced inflammation in mouse macrophages.