Antiarthritis Effect of Morin is Associated with Inhibition of Synovial Angiogensis

Morin, a flavonoid isolated from Morus alba L. (Moraceae), possesses anti-inflammatory, antiangiogenic among other biological activities. This study investigated its effect on type II collagen-induced arthritis (CIA) in rats and explored the underlying mechanisms in view of synovial angiogenesis. Morin administered po attenuated arthritic progression as indicated by reduction of arthritis scores and paw swelling. It also markedly reduced serum levels of the proinflammatory cytokines, tumor necrosis factor alpha (TNF-α) and interleukin-6 (IL-6), but increased the level of anti-inflammatory cytokine interleukin-10, and ameliorated histopathological changes of joints. Morin markedly inhibited expression of CD31, vascular endothelial growth factor (VEGF), and basic fibroblast growth factor in synovial membrane tissues, and decreased serum levels of VEGF in CIA rats. In vitro, morin markedly inhibited VEGF-induced migration and tube formation in human umbilical vein endothelial cells. These results indicate that morin had antirheumatoid potential, and its mechanism might be associated with inhibition of synovial angiogenesis.