Therapeutic effects of the endothelin receptor antagonist Ro 48-5695 in the TNBS/DNBS rat model of colitis

OBJECTIVE: Endothelins can act as polyfunctional cytokines. It is therefore possible that endothelins could play an active role in gut inflammation. Elevated levels of endothelin-1 have been reported in ulcerative colitis and Crohn's disease. The aim of this study was to establish the therapeutic effect of a 'new' endothelin receptor antagonist Ro 48-5695 in an animal model of inflammatory bowel disease. This study compares the effect of Ro 48-5695 on colonic damage induced by two haptens: trinitrobenzenesulphonic (TNBS) or dinitrobenzenesulphonic acid (DNBS). METHODS: Colitis was induced by intra-rectal administration of TNBS or DNBS. After TNBS/DNBS injury, rats were treated with 10.0, 3.0, 1.0 or 0.3 mg/kg of Ro 48-5695 orally, daily for 5 days. On day 6 post-hapten treatment, colonic tissues were removed and examined in a blinded fashion for macroscopic damage (damage score) and myeloperoxidase (MPO) activity. Stool consistency and adhesions were also measured. RESULTS: Oral administration of Ro 48-5695 almost completely prevented TNBS-induced damage at a dose of 10 mg/kg. The same dose in this model also had a therapeutic effect as measured by MPO and incidence of diarrhoea and adhesions. In DNBS-induced colonic damage, Ro 48-5695 was more potent and at 1.0 and 3.0 mg/kg decreased the damage score by 50 and 60% respectively; also the incidence of adhesions and diarrhoea was significantly reduced. However, MPO activity in this model was affected only by the highest dose of Ro 48-5695 tested (3.0 mg/kg) where it was reduced by 48%. CONCLUSIONS: These data provide evidence for the involvement of endothelins in the pathophysiology of inflammatory bowel disease and support the possibility of exploring a new therapeutic approach.