Critical role of MCP-1 in the pathogenesis of experimental colitis in the context of immune and enterochromaffin cells

Mucosal changes in inflammatory bowel disease (IBD) are characterized by ulcerative lesions accompanied by a prominent infiltrate of inflammatory cells including lymphocytes, macrophages, and neutrophils and alterations in 5-hydroxytryptamine (5-HT)-producing enterochromaffin (EC) cells. Mechanisms involved in recruiting and activating these cells are thought to involve a complex interplay of inflammatory mediators. Studies in clinical and experimental IBD have shown the upregulation of various chemokines including monocyte chemoattractant protein (MCP)-1 in mucosal tissues. However, precise information on the roles of this chemokine or the mechanisms by which it takes part in the pathogenesis of IBD are not clear. In this study, we investigated the role of MCP-1 in the development of hapten-induced experimental colitis in mice deficient in MCP-1. Our results showed a significant reduction in the severity of colitis both macroscopically and histologically along with a decrease in mortality in MCP-1-deficient mice compared with wild-type control mice. This was correlated with a downregulation of myeloperoxidase activity, IL-1beta, IL-12p40, and IFN-gamma production, and infiltration of CD3+ T cells and macrophages in the colonic mucosa. In addition, we observed significantly lower numbers of 5-HT-expressing EC cells in the colon of MCP-1-deficient mice compared with those in wild-type mice after dinitrobenzenesulfonic acid. These results provide evidence for a critical role of MCP-1 in the development of colonic inflammation in this model in the context of immune and enteric endocrine cells.

The putative role of endogenous and exogenous opiates in inflammatory bowel disease

The mu opioid receptor (MOR) is upregulated in inflammatory bowel disease, prompting consideration of the development of selective MOR agonists for the treatment of inflammatory bowel disease

Induction of a fibrogenic response in mouse colon by overexpression of monocyte chemoattractant protein 1

BACKGROUND AND AIMS

Monocyte chemoattractant protein 1 (MCP-1) is increased transmurally in inflammatory bowel disease (IBD). Although MCP-1 is considered to play an important role in fibrotic disease in other organs, the role of MCP-1 in gut fibrosis is unknown. We investigated the fibrotic potential of MCP-1 in the gut by overexpressing this chemokine in the mouse colorectal wall.

METHODS

Intramural gene transfer by direct injection of adenovector into the mouse rectal wall was established. C57BL/6 and Rag2(-/-) (B and T cell deficient) mice received 2.5 x 10(9) plaque forming units of an adenovector encoding murine MCP-1 (AdMCP-1) or control virus (AdDL70) via intramural injection. Mice were killed at various time points and tissues were obtained for histopathological and biochemical analysis.

RESULTS

AdMCP-1 significantly increased collagen production in the colorectum and this was associated with significant elevation of transforming growth factor beta (TGF-beta) and tissue inhibitor of metalloproteinase (TIMP-1) protein. Transmural collagen deposition was observed after AdMCP-1 administration, and was accompanied by CD3+ T cells, F4/80+ macrophages, and vimentin+ cell infiltrates. Collagen was differentially distributed, with type I deposited in the muscularis mucosa and muscularis propria and type III in the submucosa and myenteric plexus. AdMCP-1 failed to induce collagen overproduction in immunodeficient Rag2(-/-) mice.

CONCLUSION

These findings suggest that MCP-1 can induce fibrosis in the gut and that this process involves interaction between T cells and vimentin positive fibroblasts/myofibroblasts, as well as the subsequent upregulation of TGF-beta and TIMP-1 production. This model provides a basis for considering MCP-1 in the pathogenesis of strictures in IBD.

Specific probiotic therapy attenuates antibiotic induced visceral hypersensitivity in mice

BACKGROUND AND AIMS

Abdominal pain and discomfort are common symptoms in functional disorders and are attributed to visceral hypersensitivity. These symptoms fluctuate over time but the basis for this is unknown. Here we examine the impact of changes in gut flora and gut inflammatory cell activity on visceral sensitivity.

METHODS

Visceral sensitivity to colorectal distension (CRD) was assessed at intervals in healthy mice for up to 12 weeks, and in mice before and after administration of dexamethasone or non-absorbable antibiotics with or without supplementation with Lactobacillus paracasei (NCC2461). Tissue was obtained for measurement of myeloperoxidase activity (MPO), histology, microbiota analysis, and substance P (SP) immunolabelling.

RESULTS

Visceral hypersensitivity developed over time in healthy mice maintained without sterile precautions. This was accompanied by a small increase in MPO activity. Dexamethasone treatment normalised MPO and CRD responses. Antibiotic treatment perturbed gut flora, increased MPO and SP immunoreactivity in the colon, and produced visceral hypersensitivity. Administration of Lactobacillus paracasei in spent culture medium normalised visceral sensitivity and SP immunolabelling, but not intestinal microbiota counts.

CONCLUSION

Perturbations in gut flora and in inflammatory cell activity alter sensory neurotransmitter content in the colon, and result in altered visceral perception. Changes in gut flora may be a basis for the variability of abdominal symptoms observed in functional gastrointestinal disorders and may be prevented by specific probiotic administration.