Anti-inflammatory effects of 5-aminosalicylic acid conjugates with chenodeoxycholic acid and ursodeoxycholic acid on carrageenan-induced colitis in guinea-pigs

Two epimeric bile acid conjugates, 5-aminosalicylic acid-chenodeoxycholic acid (5-ASA-CDCA) and 5-aminosalicylic acid-ursodeoxycholic acid (5-ASA-UDCA), were synthesized to deliver 5-ASA to the large intestine by oral administration. The movement of the conjugates down the gastrointestinal tract and the anti-inflammatory effects on ulcerative colitis were investigated by administering the conjugates to guinea-pigs with an inflammatory bowel disease induced by 2% degraded carrageenan solution. The conjugates were protected from deconjugation in stomach and small intestine and reached the caecum and the colon, where 5-ASA was more easily liberated from 5-ASA-CDCA than from 5-ASA-UDCA. The conjugates at doses equivalent to 50 or 150 mg kg(-1) 5-ASA were orally administered once a day for 4 weeks from the 15th day after starting carrageenan treatment. The body weights and the bleeding scores of occult blood in faeces were measured during the experiment. The number of ulcers in the caecum and the colon were counted after killing the guinea-pigs at the end of the experiment. Rapid onset of efficacy was shown by a significant reduction in bleeding scores within a week after administration of the conjugates. Treatment with the lower dose of 5-ASA-CDCA showed a recovery of body weight and a significantly decreased number of ulcers in the caecum, and the ulcers in the colon had completely disappeared by the end of the experiment. There was a good correlation found between the number of ulcers in the caecum and the bleeding scores of occult blood in faeces. The findings indicate that both conjugates were sufficiently delivered to the large intestine without deconjugation and that the lower dose of 5-ASA-CDCA is enough for treatment of ulcerative colitis; in colonic inflammatory bowel diseases.