Final Progress Report

Proposal No.   IBD-0038
Principal Investigator: Torsten Kucharzik, M.D.
Applicant Organization: University Hospital of Münster (Germany)
Project Title: Role of alpha-MSH and related tripeptides as potential anti-inflammatory agents during inflammatory bowel disease
Period of Award: January 1, 2003 - December 31, 2004

Summary of project aims

   1.    To determine the effect of a-MSH (1-13 and 11-13) on intestinal epithelial cells and to determine its expression and signal transduction pathways in intestinal epithelial cells

   2.    To evaluate the role of alpha-MSH and its related tripeptide (a-MSH (11-13), KPV) in prevention or attenuation of experimental colitis?

   3.    To determine the relevance of melanocortin-receptors during inflammatory bowel disease

    a)      Tissue expression of melanocortin receptors in patients with chronic IBD

    b)      Does MC1R mediate the antiinflammatory activity of a-MSH and KPV in intestinal epithelial cells?

Accomplishments towards meeting those aims

As the list of our results that we obtained during the funded period clearly shows, we had been able to answer most of the questions that we had when we started our project. In particular, we could determine the immunoregulatory effects of α-MSH on intestinal epithelial cells and could describe an autoregulatory loop that may be of great importance to maintain homeostasis in the intestinal mucosa. We could further demonstrate that α-MSH as well as the small α-MSH derived tripeptide, KPV, are strong inhibitors of inflammation in two murine models of IBD and are therefore strong candidates for new therapies in human IBD. We could also demonstrate that the main receptor for both molecules is the melanocortin-1 receptor (MC1R) which seems to play a crucial role during intestinal inflammation as functional deletion of the receptor exerts strong aggravation of inflammation in mice. Our project therefore opens new directions for future projects that will determine molecules that bind and stimulate the MC1R and may thereby control intestinal inflammation.

Taken together, we received very promising results during the funded period that will probably enable us to continue the projects with the help of other funding agencies in the future.

A list of significant results (positive or negative)

Aim 1:

Constitutive expression of POMC, the prohormone of α-MSH, as well as MC1R in three intestinal epithelial cell lines (Caco-2, HT29, T84)
Secretion of α-MSH by intestinal epithelial cells upon stimulation with proinflammatory cytokines
Significant dose-dependent down regulation of cytokine-induced respectively constitutive epithelial IL-8 secretion by α-MSH and KPV (autoregulatory loop in intestinal epithelial cells)
Effect of α-MSH on intestinal epithelial cells is cAMP dependent
Human intestinal epithelial cells constitutively express MC1R protein in vitro and in vivo

Aim 2:

Alpha-MSH given i.p. can prevent DSS colitis in mice
The α-MSH derived tripeptide KPV given i.v. and i.p. is capable to attenuate DSS-colitis as well as transfer colitis in mice
KPV is capable to attenuate Citrobacter rodentium induced colitis in mice
KPV has no therapeutic effect in mice with non-functional MC1R (MC1R e/e) suggesting that the melanocortin-1 receptor (MC1R) is relevant for mediating the antinflammatory effects of KPV

Aim 3:

Melanocortin-receptor 1 (MC1R) as well as MC2R and MC5R are expressed by intestinal epithelial cells
Strong up-regulation of MC1R expression in the mucosa of patients with Crohn’s disease and ulcerative colitis (predominantly in intestinal epithelial cells)
Severe aggravation of colitis in mice with non-functional MC1R (MC1R e/e) in two different models of murine colitis (DSS colitis and Citrobacter rod. induced colitis)
MC1R e/e / C57BL6 bone marrow chimera experiments revealed that non-hematopoetic cells bearing MC1R are responsible for protection against murine colitis (DSS colitis). Data suggest a pivotal role of non-hematopoetic cells expressed MC1R in the host defense response to inflammatory stimuli

Taken together, we could demonstrate that α-MSH is an important inflammatory mediator that is not only expressed by hematopoetic cells but also by intestinal epithelial cells. Epithelial cell secreted α-MSH acts through binding on epithelial cell expressed MC1R in an autoregulatory fashion.

We could further demonstrate that α-MSH as well as its derived tripeptide, KPV, is capable to down-regulate intestinal inflammation in two murine models of experimental colitis. Both peptides may therefore act as new, inexpensive treatment options for patients with inflammatory bowel disease.

We could further show that the relevant receptor for α-MSH, the melanocortin-receptor-1 plays a crucial role during experimental colitis. Agonistic stimulation of MC1R may therefore be useful as new therapy for inflammatory bowel disease in the future.

Lay Summary

Alpha-melanocyte-stimulating-hormone (α-MSH) is an endogenous neuroimmunomodulatory peptide that has been shown to have potent antiinflammatory properties in a variety of animal disease models as well as in cell culture experiments. The aim of our project was to evaluate α-MSH regarding its potential use as antiinflammatory agent for treatment of inflammatory bowel disease (IBD).

We demonstrated that α-MSH is an important anti-inflammatory agent that is produced by epithelial cells of the gastrointestinal tract and responsible for immune homeostasis in the intestinal mucosa. We further demonstrated that α-MSH and, in particular, its derived small tripeptide KPV, has strong antiinflammatory properties in two experimental models of inflammatory bowel disease. Both agents are capable of downregulating intestinal inflammation and may therefore be useful as therapeutic agents for patients with chronic active inflammatory bowel disease. The use of these peptides for IBD treatment is now going to be determined in clinical trials. We further demonstrated that the relevant receptor for α-MSH, the melanocortin receptor-1 (MC1R), plays an unexpected and pivotal role during intestinal inflammation in mice, as deletion of this receptor causes severe aggravation of colitis in mice. Development of new peptides with agonistic stimulation of the MC1-receptor may therefore be useful as an additional treatment option for patients with IBD.

Taken together, results from our project moved major steps forward in: i) understanding the role of these modulating peptides in the intestinal immune system, ii) in determining KPV as a new, well tolerated and inexpensive potential treatment option for patients with chronic active IBD and iii) in opening new directions for future research projects that may establish new therapeutic agents that bind and stimulate the melanocortin receptor-1 and may be useful to treat patients with IBD.

Last updated 07/22/2010