SummaryInflammatory bowel diseases are chronic inflammatory disorders of the gastrointestinal tract. Vasoactive intestinal peptide (VIP) is a neuropeptide with known anti-inflammatory activity. We have demonstrated previously that administration of VIP inhibits leucocyte migration in a murine model of delayed-type hypersensitivity, and anti-inflammatory efficacy is supported by other studies. The aim of this study was to investigate the VIP effects in a murine model of intestinal inflammation. Colitis was induced in BALB/c mice by a 2·5 mg enema of 2,4,6-trinitrobenzenesulphonic acid (TNBS) and the mice were killed on day 7. Mice were administered either a 3-day (therapeutic) or 7-day (prophylactic) constant infusion of VIP by subcutaneously implanted mini-osmotic pumps, or intraperitoneal (i.p.) injection of VIP on alternate days over 7 days. Clinical disease scores, weight changes, histopathology of colon tissues, plasma VIP levels, cytokine levels and chemotaxis of peripheral blood mononuclear cells were evaluated. After administration of TNBS, mice quickly developed severe colitis accompanied by dramatic body weight loss (20% by day 6) and high mortality (30%). Prophylactic treatment using high-dose VIP abrogated leucocyte chemotaxis; however, it failed to ameliorate the weight loss and mortality. Moreover, VIP delivered either by constant infusion or i.p. failed to modify the clinical, histological or cytokine markers of disease. Our studies show that, despite an ability to inhibit chemokine-induced chemotaxis of mononuclear cells, VIP was unable to modulate TNBS-induced colitis. This contrasts with the efficacy of VIP in models of mild inflammatory disease and suggests that VIP is unlikely to provide a useful model for novel anti-IBD therapy.

Background and aims: Chemokine receptors are key determinants of leucocyte trafficking. While the chemokine receptor CCR9 and its chemokine ligand CCL25 (TECK) mediate lymphocyte homing to the healthy small intestine, the chemokine receptors important for recruitment during intestinal inflammation are undefined. Animal studies have suggested potential roles for CCR2 and CCR5 in inflammatory bowel disease (IBD). The aim of this study was to understand the role of CCR2 in human IBD. Methods: Resections of ileum or colon were obtained from patients undergoing surgery for small bowel Crohn's disease (SBCD; n = 10), Crohn's colitis (n = 5), ulcerative colitis (n = 6), and non-IBD related conditions (control ileum n = 11; control colon n = 11). Expression of CCR2 by lamina propria lymphocytes (LPLs) was determined by both flow cytometry and immunohistochemistry. As a functional correlate, chemotaxis assays using the CCR2 ligand, CCL2 (MCP-1), were performed. Expression of CCR2 by peripheral blood lymphocytes was determined by flow cytometry. Results: There were greater than 30-fold more CCR2+ LPLs in SBCD than in control ileum (29.3% (19.9-55.1) v 0.9% (0.4-11.5); p = 0.0007). Specifically, CCR2

Chemokines mediate trafficking of leukocytes to sites of inflammation and immune responses through activation of G protein-coupled receptors, which thereby provide appealing targets for novel anti-inflammatory agents. Vasoactive intestinal peptide (VIP) is an immunosuppressive neurotransmitter. We show that VIP inhibited the function of chemokine receptors on monocytes and CD4+ T lymphocytes, with impaired chemotaxis and calcium flux in response to the cognate chemokine ligands CXCL12, CCL3, CCL4, and CCL5. This was mediated by VIP receptor type 1 and was not caused by chemokine receptor internalization. However, VIP caused dose-dependent phosphorylation of the chemokine receptor CCR5. This trans-deactivation process was studied in a murine model of delayed-type hypersensitivity: continuous infusion of VIP resulted in significant abrogation of monocyte and lymphocyte infiltration. Circulating mononuclear cells from VIP-infused mice were unable to respond to chemokines. VIP may provide a novel approach to treatment of inflammatory diseases through inhibition of chemokine-dependent leukocyte recruitment.