AIM: To investigate the effect of 4-aminosalicylic acid (4-ASA) on trinitrobenzene sulfonic acid (TNBS) -induced colitis
in rats and to clarify the related mechanism. METHODS: Colitis was induced in female SD rats by rectal administration of TNBS resolved in ethanol. The colitis rats were treated with 4-ASA-Na with doses of 100 and 200 mg/kg respectively for 2 weeks. 5-aminosalicylic acid (5-ASA) and normal saline were used as control groups. The colonic inflammation including macroscopic and histological changes and myeloperoxidase (MPO) activity was evaluated.
Superoxide dismutase (SOD) activity and malondialdehyde (MDA) level in colonic mucosa were detected by biochemical methods. The expressions of interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) mRNAs in colonic mucosa were determined by a reverse transcription polymerase chain reaction (RT-PCR) method. RESULTS: Compared with TNBS control group, the macroscopic and histological scores and MPO activity in 4-ASA treated groups were decreased (P<0.05), SOD activity was increased (P<0.05), and the level of MDA in colonic mucosa was reduced
significantly (P<0.05). The expressions of IL-1β and TNF-α mRNAs in colonic mucosa were also decreased significantly (P<0.05). The intracolonic administration with 4-ASA had no more therapeutic effect than topical treatment with 5-ASA. CONCLUSION: The topical treatment with 4-ASA can significantly attenuate the colonic damage in TNBS -induced colitis in rats and it may be related to the antioxidant mechanism and the inhibition of the expression of pro- inflammatory cytokines including IL-1β and TNF-α.