Indirubin inhibits the migration, invasion, and activation of fibroblast-like synoviocytes from rheumatoid arthritis patients.

Objectives: To evaluate the inhibition of indirubin in FLSs migration, invasion, activation, and proliferation in RA FLSs.

Methods: The levels of IL-6 and IL-8 in cultural supernatants were measured by ELISA. RA FLS migration and invasion in vitro were measured by the Boyden chamber method and the scratch assay. Signal transduction protein expression was measured by western blot. FLS proliferation was detected by Edu incorporation. F-actin was measured by immunofluorescence staining.

Results: We found that indirubin reduced migration, invasion, inflammation, and proliferation in RA FLSs. In addition, we demonstrated that indirubin inhibited lamellipodium formation during cell migration. To gain insight into molecular mechanisms, we evaluated the effect of indirubin on PAK1 and MAPK activation. Our results indicated that indirubin inhibited the activity of PAK1 and MAPK.

Conclusions: Our observations suggest that indirubin may be protective against joint destruction in RA by regulating synoviocyte migration, invasion, activation, and proliferation.