Objective To investigate the effects of 4-aminosalicylic acid (4-ASA) on rats with 2,4,6-trinitrobenzenesulfonic acid-induced colitis in order to understand its mechanisms in treatment of inflammatory bowel disease (IBD). Methods Thirty SD rats were given 2,4,6-trinitrobenzenesulfonic acid to induce colitis and were divided into model group, 5-ASA (200 mg/kg) treated group and 4-ASA (200 mg/kg) treated group with 10 each. Another 10 rats were severed as normal control. Seven days later,all animals were sacraficed for estimation of colonic tissues. The iNOS and serum level of interleukin (IL)-8 were detected by immunohistochemistry and enzyme-linked immunosorbent assay (ELISA) ,respectively. And the apoptosis of polymorphonuclear neutrophil (PMN) was examined by flow cytometry. Results In comparison with model group, the body weight was increased in rats treated with 4-ASA (t= 14.09,P<0.01), whereas the macroscopic and histological scores and MPO activity were decreased (t=7.87,18.37,6.66 and 19.60,respectively, all P values <0.01), which were similar to 5-ASA treated group (all P values > 0. 05). The expression of tissue iNOS was 73.55%±5.15% in model group, which was higher than that in control group [(5.95±1.45)% ,t=39.93,P<0.01)],but was lower than that in 5-ASA treated group [(37.80±3.82)%,t = 17.62,P<0.01] and 4-ASA treated group [(42.27±3.52) %, t= 15.76 ,P<0.01]. The serum level of IL-8 in model group was significantly higher than that in 5-ASA treated group and 4-ASA treated group (P<0. 01). The apoptosis of PMN in model group was lower than that in control group (t= 11.48,P<0.01), but higher than that in 5-ASA treated group (t= 7.51, P<0.01) and 4-ASA treated group (t= 10.47,P<0.01). Conclusions The efficacy of 4-ASA in treatment of IBD may be related to the mechanisms of reducing the migration and the activities of PMN, up-regulating PMN apoptosis and scavenging reactive oxygen radicals produced by PMN.

Objective To investigate the effects of Gefarnate on expression of myeloperoxidase (MPO),cyelooxygenase-1 (COX-1) and COX-2 in trinitrobenzene sulphonic acid (TNBS) induced experimental colitis in rats and its therapeutic effects on ulcerative colitis. Methods Forty female Sprague-Dawley (SD) rats were randomly divided into 4 groups with 10 each. The rats in group A, B and C were infused with TNBS/alcohol by enema. After the production of colitis, the rats in group A or B were treated daily with 1 ml of normal saline or with 1 ml of 5-ASA (100 mg/kg) by enema,and those in group C were treated daily with 1 ml of Gefarnate by gavage. Group D was served as normal control. After the production of colitis,animals were sacrificed at day 7 and 14 with 5 in each group. The macroscopic changes of the colon were evaluated according to disease activity index (DAD scoring and histological change was assessed by HE staining. MPO activity of the mucosa was detected by biochemical methods. Expressions of COX-1 and COX-2 in tissues were detected by immunohistochemistry. Results Compared with group A, macroscopic and histological scores and MPO activity were significantly decreased in group B and C (P<0.05). The expressions of COX-1 at day 7 and 14 were 1.86±0.51 and 1.96±0.41 in group B, 1.73±0.68 and 1.79±0.6 in group C, 1.91±0.34 and 1.99±0.45 in group D, respectively, which were significantly higher than those in group A (0.87±0.18 and 0.93±0.15, P<0.05). Whereas the expressions of COX-2 at day 7 and 14 were 1.53±0.19 and 0.73±0.15 in group B, 1.73±0.94 and 0.86±0.29 in group C, 0.24±0.18 and 0.18±0. 16 in group D, respectivley, which were significantly lower that those in group A (3.50±0.2;3 and 3.06±0.27). There was a significant difference between group D and group B or C (P<0.05). Conclusions Gefarnate provides a therapeutic effect during TNBS-induced colitis in rats, which is similar to that of 5-ASA. The mechanisms are involved in decreasing the concentration of colonic MPO and regulating the expression of COX-1/COX-2.