Inhibition of type II collagen-induced arthritis in rats by triptolide.

The effects of purified triptolide, a diterpenoid triepoxide compound derived from the Chinese traditional anti-rheumatic medicinal plant extract, Tripterygium wilfordii Hook f (TWHf), were determined in type II collagen-induced arthritis (CIA) in rats. Lewis rats were immunized with bovine type II collagen and treated with purified triptolide 0.1 mg/kg/day or control (vehicle for triptolide) by daily gavage feedings for 28 days. Triptolide was well-tolerated with no evidence of toxicity. Treatment with triptolide resulted in significant delay in time to onset of arthritis (P = 0.039), as well as significantly decreased arthritis incidence (P = 0.024), clinical arthritis severity score (P < 0.0001), histopathological arthritis severity score (P < 0.0001), and in vivo cell-mediated immunity to collagen (P = 0.0004). Triptolide appeared to be a potent immunomodulatory inhibitor of CIA in rats and this may account for the previously observed anti-rheumatic properties of crude extracts of TWHf, although more extensive studies will be needed to confirm these effects.