Protective effect of avicularin on rheumatoid arthritis and its associated mechanisms.

The present study aimed to investigate the effect of avicularin on rheumatoid arthritis (RA) in vitro, and additionally explore the molecular mechanism. To perform this investigation, an in vitro model of RA was established by treatment of the human RA synovial MH7A cell line with tumor necrosis factor-α (TNF-α). MH7A cells were then treated with various concentrations (10, 30, 100 and 300 µM) of avicularin. Then, the levels of inflammatory factors [interleukin (IL)-1β, IL-6, IL-8, matrix metalloproteinase (MMP)-1 and MMP-13] were measured by ELISA. Cell viability and apoptosis were detected using an MTT assay and flow cytometry, respectively. In addition, the expression levels of genes and proteins were determined reverse transcription quantitative polymerase chain reaction and western blot analysis. The results of the present study indicated that avicularin significantly decreased the levels of inflammatory factors (IL-1β, IL-6, IL-8, MMP-1 and MMP-13), previously increased by TNF-α, in a dose-dependent manner. Concurrently, avicularin inhibited the mRNA and protein expression levels of iNOS and COX-2 increased by TNF-α. It was also identified that TNF-α administration significantly promoted MH7A cell viability and inhibited cell apoptosis, and avicularin treatment dose-dependently inhibited MH7A cell viability and induced cell apoptosis. In addition, these data suggested that avicularin prevented the activation of the mitogen-activated protein kinase kinase (MEK)/nuclear factor kappa light-chain-enhancer of activated B-cells (NF-κB) pathway activated by TNF-α. Taken together, these results demonstrated that avicularin may inhibit the inflammatory response, prevent cell viability and induce apoptosis in human RA synovial cells through preventing the activation of the MEK/NF-κB pathway.