Anthraquinone-2,6-Disulfonic Acid as a Disease-modifying Osteoarthritis Drug An In Vitro and In Vivo Study

Pharmacologic treatment of osteoarthritis has been confined mostly to analgesic or nonsteroidal antiinflammatory drugs that only modify the symptoms. We asked whether anthraquinone-2,6-disulfonic acid might act as a disease-modifying osteoarthritis drug. We evaluated the in vitro inhibitory effect of anthraquinone-2,6-disulfonic acid on cathepsin B activity and proteoglycan release from cultured rabbit cartilage challenged with interleukin-1β in comparison with diacerhein, the prodrug of rhein. We studied the in vivo activity in an experimental osteoarthritis model induced by medial monolateral meniscectomy in rabbits. After 3 months of treatment with oral anthraquinone-2,6-disulfonic acid or diacerhein at 25 mg/kg/day, the animals were sacrificed and the knees were retrieved; cluster chondrocytes, fibrillations, fissures, and osteophytes were studied on cartilage biopsies. The evidence for disease-modifying activity of anthraqui-none-2,6-disulfonic acid was (1) the in vitro dose-dependent inhibition of cathepsin B activity, (2) the in vitro time- and dose-dependent inhibition of interleukin-1β-stimulated proteoglycan release from the cartilage matrix, and (3) the in vivo reduction of all cartilage degeneration parameters. Our data suggest anthraquinone-2,6-disulfonic acid is worth exploring for treating osteoarthritis.