Taraxasterol is an effective component of dandelion that has anti-inflammatory 
effects in vivo and in vitro. The present study was performed to explore whether 
taraxasterol exhibits a protective effect against rheumatoid arthritis through 
the modulation of inflammatory responses in mice. Eight-week-old CCR9-deficient 
mice were injected with a collagen II monoclonal antibody cocktail to create a 
rheumatoid arthritis model. In the experimental group, arthritic model mice were 
treated with 10 mg/kg taraxasterol once per day for 5 days. Treatment with 
taraxasterol significantly increased the pain thresholds and reduced the 
clinical arthritic scores of the mice in the experimental group compared with 
those of the model group. Furthermore, treatment with taraxasterol significantly 
suppressed tumor necrosis factor-α, interleukin (IL)-1β, IL-6 and nuclear 
factor-κB protein expression levels compared with those in the rheumatoid 
arthritis model mice. Taraxasterol treatment also significantly reduced nitric 
oxide, prostaglandin E2 and cyclooxygenase-2 levels compared with those in the 
rheumatoid arthritis model group. These observations indicate that the 
protective effect of taraxasterol against rheumatoid arthritis is mediated via 
the modulation of inflammatory responses in mice.