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. (C) 2008 International Federation for Cell Biology. Published by Elsevier Ltd. All rights reserved.