Chronic administration of galanin attenuates the TNBS-induced colitis in rats E. Talero a , S. Sánchez-Fidalgo a , J.R. Calvo b , V. Motilva a, ⁎ a Department of Pharmacology, School of Pharmacy, University of Seville, C. Prof. Garcia Gonzalez no. 2, 41012 Seville, Spain b Department of Medical Biochemistry and Molecular Biology, School of Medicine, University of Seville, Seville, Spain Received 21 July 2006; received in revised form 14 December 2006; accepted 21 December 2006 Available online 19 January 2007 Abstract 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. © 2007 Elsevier B.V. All rights reserved. Keywords: Peptides; Galanin; IBD; Inflammatory colitis; TNBS; iNOS; COX-2; Mast cell 1. Introduction IBD is considered a chronic recurrent inflammatory disorder characterized by the development of intestinal inflammation resulting from the transmural infiltration of neutrophils, macrophages, lymphocytes and mast cells, ultimately giving rise to mucosal disruption and ulceration [1]. This pathology is especially high in Western countries and, although its aetiology is still not well known, genetic, environmental signals such as stress, and immunologic influences, may all contribute to the disease process. In the TNBS, the chronic intestinal inflammation induced after its intracolonic administration resembles many of the clinical, histopathological and immune characteristics of IBD in humans. Infiltrated granulocytes and macrophages produce high levels of pro-inflammatory cytokines, such as tumour necrosis factor-α (TNF-α), clearly involved in the pathogenesis of IBD. Among immune mediators, mast cells may play an important role in the recovery of the intestinal dysfunction, and although its involve- ment is still little understood, different proteases and other cellular products liberated in function of their considerable heterogeneity could play a key role, especially in more advanced states of the reparative process [2–7]. Another mediator that has been closely associated with the initiation and maintenance of intestinal inflammation in IBD is NO, generated by the up-regulation of the enzyme iNOS in epithelial cells. Its excessive production exacerbates the pathological features by different mechanisms, including direct cytotoxicity, activation of neutrophils, vasodila- tion, reduction of smooth muscle tone, increased production of Regulatory Peptides 141 (2007) 96 – 104 www.elsevier.com/locate/regpep ⁎ Corresponding author. Tel.: +34 954 556503; fax: +34 954 233765. E-mail address: motilva@us.es (V. Motilva). 0167-0115/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.regpep.2006.12.029