Chronic administration of galanin attenuates the TNBS-induced colitis in rats

Inflammatory bowel disease (IBD) is a chronic intestinal inflammatory disorder considered as a consequence of an aberrant response of the immune system to luminal antigens. Numerous groups of agents are being evaluated as novel therapeutic approaches for its treatment; in this way, different peptides have emerged as potential candidates. Galanin is an active neuropeptide distributed in the central and periphery nervous systems although it has been also described having important autocrine and paracrine regulatory capacities with interesting inflammatory and immune properties. In this line, we have observed that galanin treatment has a significant preventive effect in the experimental trinitrobenzensulfonic acid (TNBS) acute model of inflammatory colitis. The aim of the present study was to investigate intensively the role played by the peptide in the evolution of the inflammatory pathology associated to IBD. Galanin (5 and 10 μg/kg/day) was administered i.p., daily, starting 24 h after TNBS instillation, and continuing for 14 and 21 days. The lesions were blindly scored according to macroscopic and histological analyses and quantified as ulcer index. The results demonstrated that chronic administration of galanin improved the colon injury than the TNBS induced. The study by Western-blotting of the expression of nitric oxide inducible enzyme (iNOS), as well as the total nitrite production (NO) assayed by Griess-reaction, showed significant reduction associated with peptide administration. The number of mast cells was also identified in histological preparations stained with toluidine blue and the results showed that samples from galanin treatment, mostly at 21 days, had increased the number of these cells and many of them had a degranulated feature. In conclusion, chronic administration of galanin is able to exert a beneficial effect in the animal model of IBD assayed improving the reparative process. Participation of nitric oxide pathways and mucosal mast cells can not be discarded.