Luteolin inhibits proliferation and affects the function of stimulated rat synovial fibroblasts

Hyperproliferation of synovial fibroblasts is considered to be a pivotal event in the pathogenesis of rheumatoid arthritis (RA). Luteolin, a flavonoid, inhibits the proliferation of synovial fibroblasts in collagen-induced arthritic rats. Treatment with luteolin also decreases the secretion of matrix metalloprotease-1 and -3 and the expression of IL-6, IL-8, IL-15, and TGF-beta. Luteolin treatment caused a delay of cells in the G(2)/M phase. Interestingly, combination treatment with luteolin and TNF-alpha exhibited a synergistic inhibitory effect in all experiments. Western blotting demonstrated that treatment with luteolin alone or combined with TNF-alpha inhibited the MAPK/ERKs and PI3K-Akt pathways. These results indicate that luteolin inhibits the proliferation and partially blocks the pathogenic function of synovial fibroblasts in rheumatoid arthritis.