Abstract:
In this study, we investigated the anti-inflammatory effect and mechanism of tilianin in lipopolysaccharide (LPS)-induced RAW264.7 cells. The cell viability was detected by cell counting kit-8 (CCK-8) assay. The content of tumor necrosis factor
α (TNF-
α) and interleukin-6 (IL-6) were detected by enzyme-linked immuno sorbent assay (ELISA) kits. The content of nitric oxide (NO) was assayed by Griess reagent method. The level of intracellular reactive oxygen species (ROS) was detected by 2', 7'-dichlorodihydrofluorescein diacetate (DCFH-DA) fluorescent probe. The protein levels of Toll like receptor 4 (TLR4), myeloid differentiation primary response gene 88 (Myd88), nuclear factors
κB p65 (NF-
κB p65), phosphorylated nuclear factor
κB p65 (p-NF-
κB p65), nuclear factor
κB inhibitory protein
α (Ⅰ
κB
α) and phosphorylation nuclear factor
κB inhibitory protein
α (p-Ⅰ
κB
α) were detected by Western blot. The mRNA and protein levels of NLRP3, pro-IL-1
β, pro-IL-18 and pro-caspase-1 were detected by qRT-PCR and Western blot. Immunofluorescence staining was used to detect the nuclear translocation of NF-
κB p65. The effect of tilianin on the TLR4/Myd88/NF-
κB signaling pathway was further validated by using the TLR4 signaling inhibitor restatorvid (TAK242). The results showed that tilianin significantly reduced the levels of TNF-
α, IL-6 and NO in the supernatant of RAW264.7 cells and decreased the content of intracellular ROS. Tilianin reduced the levels of TLR4, Myd88, p-NF-
κB p65 and p-Ⅰ
κB
α protein and nuclear translocation of NF-
κB p65. Tilianin could reduce the protein levels of NLRP3, pro-IL-1
β, pro-IL-18 and pro-caspase-1. Tilianin significantly inhibited the mRNA levels of NLRP3 and pro-IL-1
β. The above research results indicated that tilianin could significantly alleviate the LPS-induced inflammatory response in RAW264.7 cells and its mechanism might be related to downregulate the TLR4/Myd88/NF-
κB signaling pathway to inhibit NLRP3 inflammasome.