Acute and chronic responses associated with adrenomedullin administration in experimental colitis.

Adrenomedullin (AM) is a 52 amino acid peptide and member of the calcitonin gene-related peptide (CGRP) super family. Given that AM has emerged as a potential immuno-regulatory and anti-inflammatory agent in various experimental models, this study has deepened into its possible therapeutic effect in intestinal inflammation analyzing the responses in both acute and chronic (14 and 21 days) phases of TNBS-induced colitis in rats. In the acute model, AM treatment reduced the incidence of diarrhea and the severity of colonic damage, and improved the survival rate at the three doses assayed (50, 100, and 200ng/kg animal). AM administration was able to reduce the early production of TNF-alpha and collaborated to maintaining basal levels of IFN-gamma and IL-10. In the chronic studies the peptide attenuated the extent of the damage with lesser incidence of weight loss and diarrhea (50 and 100ng/kg animal). Cellular neutrophil infiltration, with the subsequent increase in myeloperoxidase (MPO) levels caused by TNBS, was reduced after chronic AM administration. The peptide played a role in the evolution of Th1/Th2 cytokines balance and chronic disease recuperation: levels of proinflammatory TNF-alpha and IFN-gamma decreased and anti-inflammatory IL-10 increased significantly. Cyclooxygenase-2 (COX-2) and nitric oxide synthase (iNOS) protein expression were not modified by AM administration, although a reduction of nitric oxide (NO) production could be detected in the chronic model. These results support a role of AM as an anti-inflammatory factor with beneficial effects in intestinal inflammatory colitis.

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 microg/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.

Role of different inflammatory and tumor biomarkers in the development of ulcerative colitis-associated carcinogenesis.

BACKGROUND: Colorectal cancer (CRC) is the most severe complication in inflammatory bowel disease (IBD). In the present study we investigated different mechanistic links between chronic colonic inflammation and its progression to adenocarcinoma. Along these lines, given that adrenomedullin (AM) has been implicated in carcinogenesis, we also analyzed changes in its colonic expression. METHODS: Mice were exposed to 5, 10, and 15 cycles of dextran sulfate sodium (DSS); each cycle consisted of 0.7% DSS for 1 week followed by distilled water for 10 days. After each period, macroscopic and histological studies, as well as characterization of inflammatory and tumor biomarkers, were carried out. RESULTS: The disease activity index (DAI) showed that the disease was present from the third cycle and it gradually increased during the course of DSS treatment. Macroscopic tumors were only seen after 15 cycles, and microscopic study showed that inflammation, dysplasia, and adenocarcinomas correlated with DSS cycles. ß-Catenin and proliferating cell nuclear antigen expressions progressively increased in animals treated with the different cycles of DSS. TNF-α and IFN-γ showed the highest production at the tenth cycle. COX-2, mPGES-1, and iNOS levels were also appreciably higher at the fifth and tenth cycles. Moreover, we observed a progressive enhancement in AM expression and changes in its intracellular location during the progression of the disease. CONCLUSIONS: Our results show an early induction of proinflammatory factors, which may contribute to the development of colon cancer, as well as demonstrate, for the first time, the expression of AM in IBD-derived CRC.

Extra-virgin olive oil-enriched diet modulates DSS-colitis-associated colon carcinogenesis in mice.

BACKGROUND & AIMS: Patients with inflammatory bowel disease (IBD) are at increased risk for developing ulcerative colitis (UC)-associated colorectal cancer (CRC). Several studies have shown that extra virgin olive oil (EVOO) might possess anti-inflammatory, antiproliferative and antiapoptotic effects. We have evaluated EVOO diet effects on the severity of repeated colitis-associated CRC. METHODS: Six-week-old C57BL/6 mice were randomized into two dietary groups: sunflower oil (SFO) and EVOO diets, both at 10%. Mice were exposed to 15 cycles of 0.7% dextran sodium sulphate (DSS) for 1 week followed by distilled water for 10 days. After, the rats were sacrificed and colonic damage was both histologically and biochemically assessed. RESULTS: Disease activity index (DAI) was significantly higher on SFO vs. EVOO diet at the end of the experimental period. EVOO-fed mice showed less incidence and multiplicity of tumors than in those SFO-fed mice. ß-catenin immunostaining was limited to cell membranes in control groups, whereas translocation from the cell membrane to the cytoplasm and/or nucleus was showed in DSS-treated groups and its expression was higher in SFO-fed animals. Cytokine production was significantly enhanced in SFO-fed mice, while this increase was not significant in EVOO-fed mice. Conversely, cyclooxygenase-2 (COX-2) and inducible nitric oxidase synthase (iNOS) expression were significantly lower in the animal group fed with EVOO than in the SFO group. CONCLUSIONS: These results confirm that EVOO diet has protective/preventive effect in the UC-associated CRC. This beneficial effect was correlated with a better DAI, a minor number of dysplastic lesions, a lower ß-catenin immunoreactivity, a proinflammatory cytokine levels reduction, a non modification of p53 expression and, COX-2 and iNOS reduction in the colonic tissue.

Intestinal immunomodulation. Role of regulative peptides and promising pharmacological activities.

About 50 peptides, and a similar number of peptide receptors, are known to be present in the gut and this amount is likely to rise significantly over the next few years. While there has been a massive research effort to define their functions and their anatomical distribution in the central nervous system (CNS), the understanding of their roles in the gut is far more limited. Classically, the physiological functions include the control of motility, fluids, electrolytes, and digestive enzymes secretion, or vascular and visceral pain function, and more recently, the role-played in cell proliferation and survival, and in immune-inflammatory responses. The term inflammatory bowel disease (IBD) that encompasses Crohn's disease and ulcerative colitis, is clearly an inflammatory disease where several mediators such as cytokines, chemokines, prostanoids, nitric oxide or free radicals, produced by infiltrating cells, play a critical role in intestine tissue alteration. Some peptides, initially known for their neuroregulative properties, have been suggested to act as endogenous immune factors, with predominant antiinflammatory effects. Based on these actions, these molecules are proposed as potential agents for the treatment of IBD and selective peptide analogs are being developed as novel therapeutic strategies for IBD patients. Patients with IBD have an increased risk for developing colorectal cancer (CRC). Up to the present time, no known genetic basis has been identified to explain CRC predisposition in these IBD. Instead, it is assumed that chronic inflammation is what causes cancer. This is supported by the fact that colon cancer risk increases with longer duration of colitis, greater anatomic extent of colitis, the concomitant presence of other inflammatory manifestations, and the fact that certain drugs used to treat inflammation, may prevent the development of CRC. However, though different regulative peptides play a beneficial role in experimental IBD, an increasing number of articles about cancer pathology are starting to implicate different peptides in tumor initiation and progression. The complexities of cancer could be described in terms of a small number of underlying principles and the malignant growth is dependent upon a multi-step process including different basic essential alterations. The activities of many peptides that are overexpressed in cancer cells help them to develop several of the molecular and physiological features that are now considered the basis of malignant growth. These collective findings implicate regulative peptides, receptors, or peptide-levels modulators, as important biological targets for developing intervention strategies against intestinal immunological disorders and cancers.