Experimental Study Of New Immunosup Pressant Drugson Rat Colitis Induced By Trinitrobenzene Sulfonic Acid

Background Inflammatory bowel diseases is a chronic relapsing inflammatory disease of the gastrointestinal tract.Its pathogenesis is not completely understood.So far, advances in research have identified the interaction between genetic,infectious, immunological and environmental factors to play role in their pathogenesis.Although their exact cause remains unclear,immunological dysfunction seems to initiate a self-sustaining inflammatory process.Some IBD patients remain refractory to conventional medical treatment,while,in others,the effectiveness of drugs is limited by side-effects.The therapeutic effects of conventional drugs on IBD are not very satisfactory.To seek novel and effective drug is always the hotspot in the study of IBD. Leflunomide is of new immunosuppressant drugs and of cell and humoral immunity immunosuppressive action.Leflunomide is a drug used clinically in the treatment of rheumatoid arthritis and organ transplantation and lupus nephritis and so on Leflunomide treatment of IBD is not to mention.Objective To investigate the protective effects of leflunomide on trinitrobenzene sulfonic acid(TNBS)-induced colitis in rats and to explore its possible mechanisms.We provide some experimental datas and experiences for seeking novel and effective drug of IBD.Methods Rat colitis model was induced by TNBS enema.Then the rats were randomly divided into 6 groups:normal control group,model group,5-ASA group(5-ASA,100mg/kg per day)and low-dose,middle-dose and high-dose(1.0,2.0, 4.0mg/kg per day)leflunomide-treated groups.Disease active index(DAI) was observed every day.2 weeks later the mice were killed and their colons were taken out to undergo gistologixal examination.The expression of nuclear factor NF-κBp65 (NF-κBp65) and tumor necrosis factor-α(TNF-α) and interleukin-10(IL-10)in the colonic tissues was detected by immunohistochemistry.The concent rations of blood TNF-αand Interleukin-2 and IL-10 was measured by enzyme linked immunosorbent assay(ELISA).Results Compared with the TNBS control group,the nomal control group of the damage activity index scores,common morphous damage index and tissue damadge index scores incolonic mucosa was was reduced significantly[0.00,0.50±0.28, 0.29±0.19 4.5±0.58,5.84±0.37,5.53±0.61,P＜0.05].The middle dose Lef group,the high dose Lef group and the 5-ASA group of the DAI scores,CMDI and TDI scores incolonic mucosa was reduced significantly[2.08±0.35,0.88±0.37,1.08±0.35, 1.84±0.34,1.19±0.20,1.50±0.35,1.93±0.46,1.04±0.15,1.51±0.14,P＜0.05]. Compared with the TNBS control group,the the nomal control group of expressions of NF-κBp65,TNF-αin colonic mucosa were also decreased significantly,but IL-10 in colonic mucosa was also increased significantly[7.91±0.19,184.10±16.19,81.45±20.12, 2.13±0.78,68.78±11.16 183.36±16.82,P＜0.05].The middle dose Lef group,the high dose Lef group and the 5-ASA group of expressions of NF-κBp65,TNF-αin colonic mucosa were also decreased significantly,but IL-10 in colonic mucosa was also increased significantly[4.53±0.40,104.1±13.59,148.76±16.53,3.29±0.23, 93.06±15.69,165.16±18.98,4.36±0.50,98.31±16.54,156.04±22.96,P＜0.05].In the tissue sections NF-κBp65 was positive mainly in the nucleus in the TNBS control group, NF-κBp65 was mainly positive in the cytoplasm in normal control group and all treated groups.Compared with the TNBS control group,the nomal control group of the content rations of blood TNF-αand IL-2 was decreased significantly,but the concent rations of blood IL-10 was increased significantly[66.89±7.11,60.18±6.77,26.31±7.79, 34.03±6.28,47.09±6.84,55.27±10.02,P＜0.05].The middle dose lef group,the high dose lef group and the 5-ASA group of the concent rations of blood TNF-αand IL-2 was decreased significantly,but the concent rations of blood IL-10 was increased significantly[42.99±5.15,51.52±3.91,51.00±10.01,36.76±4.87,50.56±4.12, 53.17±9.90,39.10±5.22,51.53±3.19,50.40±8.55,P＜0.05].Conclusions Leflunomide has noticeable protective effects on TNBS-induced colitis in rats,can increase the level of anti-inflammatory cytokines interleukin-10 and inhibite activation of NF-κB in the colonic mucosa of rat s with colitis and the suppression of proinflammatory cytokines may be one of its main mechanisms.