Adjuvant-induced arthritis model

Wistar rats (male, 220–250 g, Charles River-Germany) were injected intradermally at the base of the tail (100μl) with complete Freunds adjuvant containing M. tuberculosis. In this model, arthritis develops in approximately 11–12 days after injection with the adjuvant, as revealed by a severe swelling of the hind paws [24]. The rats were treated orally with FTY720 at 0.1 mg/kg QD, NIBR-0213 at 30 mg/kg BID, or its vehicle at day-5 or day-9 post-injection of complete Freund’s adjuvant, but before the onset of arthritis (n = 5–10/group). To assess the development of arthritis in each animal, the diameters of both hind paws were measured, in the medial-lateral and anterior-posterior directions, to calculate a mean paw diameter (mØ) at baseline and at termination and evaluate paw swelling as the difference between both values (ΔmØ). The inhibitory effects of NIBR-0213 treatments were expressed as % inhibition vs swelling in vehicle-treated group.