Isolation and identification of the components in Cybister chinensis Motschulsky against inflammation and their mechanisms of action based on network pharmacology and molecular docking

Cybister chinensis Motschulsky belongs to the family Dytiscidae. As a traditional Chinese medicine, the insect is called Longshi in the folk and is commonly used to treat enuresis in children and frequent urination in the elderly.Inflammation is involved in chronic kidney disease. The previous study proved ethanol extract of C. chinensis exhibited anti-inflammation effects in the Doxorubicin-induced kidney disease. However, the material basis and their possible mechanism of the insect were still unclear. Thus, we aimed to separate the active compounds of the ethanol extract from C. chinensis and to investigate their possible mechanism of anti-inflammation by network pharmacology and molecular docking.The insect was extracted with 75% ethanol to produce ethanol extracts and then were extracted by petroleum ether, ethyl acetate and n-butanol respectively. Silica gel column chromatography and preparative HPLC were applied to separate the compounds of the extract. The compounds were characterized and identified by NMR and mass. The compound associated genes were collected by BATMAN-TCM database and the inflammation associated genes were obtained through DigSee database. The protein-protein interaction (PPI) network was carried out via Search Tool for the Retrieval of Interacting Genes/Protein (STRING) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) target pathway analysis was performed in Database for Annotation, Visualization and Integrated Discovery (DAVID). The possible mechanism of compounds against inflammation was investigated by molecular docking. Finally, the anti-inflammatory effect of the representative compound was verified by the LPS-induced Raw 264.7 cell inflammatory model. TNF-α, IL-1β and IL-6 of the cell supernatants were analyzed via using ELISA kits and the key proteins in JAK2/STAT3 signaling pathway were verified via the Western blot assays.Among crude extracts from C. chinensis, ethyl acetate extract showed the obvious anti-inflammatory effects. Nine compounds were isolated from ethyl acetate extract of Cybister chinensis for the first time, including benzoic acid (1), hydroxytyrosol (2), protocatechualdehyde (3), N-[2-(4-hydroxyphenyl)ethyl]acetamide (4), (2E)-3-phenylprop-2-enoic acid (5), 3-phenylpropionic acid (6), methyl 3,4-dihydroxybenzoate (7), 1,4-diphenyl butane-2,3-diol (8) and p-N,N-dimethylaminobenzaldehyde (9). After searching in the database, 1079 compound associated genes and 467 inflammation associated genes were found. The 137 common targets covered 77 signaling pathways, in which HIF-1 signaling pathway, TNF signaling pathway, influenza A, PI3K/Akt signaling pathway, NOD-like receptor signaling pathway, MAPK signaling pathway, Toll-like receptor signaling pathway and Jak-STAT signaling pathway were important for inflammation. Molecular docking studies showed compound 1, 4, 5, 6, 7 and 8 were the potential inhibitors of JAK2 protein. In addition, the in vitro test showed compound 5 reduced the expression of tumor necrosis factor (TNF)-α, interleukin (IL)-6 and IL-1β in lipopolysaccharide (LPS)-stimulated RAW264.7 cells in a dose-dependent manner. Furthermore, it was found that compound 5 inhibited the expression of p-JAK2 and p-STAT3 in LPS-induced RAW264.7 cells in a dose-dependent manner.Based on the network pharmacology and molecular docking, the study suggested that C. chinensis could relieve the inflammation based on the multi-compounds and multi-pathways, which provided the foundation for the medicinal application of C. chinensis.