Effect of ebosin on modulating interleukin-1β-induced inflammatory responses in rat fibroblast-like synoviocytes

The interleukin-1 beta-mitogen-activated protein kinase (MAPK) and NF-kappa B signaling pathways are involved in the pathogenesis of rheumatoid arthritis. Ebosin, a novel exopolysaccharide (EPS), exhibits anti-inflammatory activity in rat collagen-induced arthritis by suppressing the production of tumor necrosis factor-alpha, interleukin-6 and interleukin-1 beta. The aim of the present study was to assess the effects of ebosin on NF-kappa B and MAPK signaling pathways mediated through interleukin-1 beta in rat fibroblast-like synoviocytes (FLSs). Western blotting showed decreased production of phosphorylated p38, JNK1, JNK2, IKK alpha, IKK beta and I kappa B in the cytoplasm and NF-kappa B in the nucleus upon ebosin treatment. The DNA-binding activity of NF-kappa B in the cell nucleus was also inhibited by ebosin treatment, as demonstrated using an electrophoresis mobility gel shift assay. Analysis of the results of the immunofluorescence assay also showed a reduced amount of NF-kappa B in the nucleus of cells affected by ebosin. These results provided evidence for the effects of ebosin on both interleukin-1 beta-mediated MAPK and NF-kappa B signaling pathways in rat FLSs. In addition, enzyme-linked immunosorbent assay demonstrated that ebosin reduces the levels of matrix metalloproteinases MMP-1 and MMP-3 and the chemokines, interleukin-8 and RANTES. Thus, the results of the present study provide further evidence for understanding the medicinal activity of ebosin at a molecular level, therefore nominating this EPS as a potential therapeutic candidate for the treatment of rheumatic arthritis.