Galanin in the trinitrobenzene sulfonic acid rat model of experimental colitis.

Neuropeptides are molecules produced by a variety of cells that modulate several biological processes and modify the activity of cells responsible either to trigger tissue damage and to promote healing in the intestine. Galanin is a neuropeptide present in enteric nerves lining the gastrointestinal tract and involved in the secretion and contractility regulation. The aim of this study is to investigate its potential therapeutic experimental use in an immunological disorder, such as experimental trinitrobenzensulfonic acid (TNBS)-induced colitis in rats. Galanin (10, 20 and 40 microg/kg/day) was administered by intraperitoneal route 48, 24 and 1 h prior to the induction of colitis and 24 h later, and the animals were sacrificed 48 h after. The lesions were blindly scored according to macroscopic and histological scales. The inflammatory response was assessed by histological analysis and by myeloperoxidase activity (MPO) and tumour necrosis factor-alpha (TNF-alpha) production. The results indicated that Galanin prevented the morphological alteration and reduced ulcer index associated with TNBS. In addition, Galanin reduced MPO and TNF-alpha values significantly. In order to elucidate some of the mechanisms, cycloxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) expression was analyzed by Western blotting. COX-2 was not modified, but iNOS protein was significantly reduced accompanied by a diminished nitrite production, in a dose-dependent manner, in comparison to the TNBS group. In conclusion, Galanin treatment has a significant preventive effect in the TNBS-induced acute model of colitis with reduction of the analyzed inflammatory parameters. Moreover, the results obtained demonstrated by the first time that Galanin administration promotes an important reduction in NO-related mechanisms.