Scientific Abstract
Proposal No. IBD-0220
Principal Investigator: Jean-Luc Desseyn, Ph.D.
Applicant Organization: INSERM (Institut National de la Santé et de la Recherche Médicale) (Lille, France)
Project Title: Protective action of a cysteine-rice mucin domain on the intestinal mucosa in experimental colitis
Period of Award: February 1, 2008 – March 31, 2010
It is postulated that IBD result from an inappropriate and ongoing activation of the immune system due to contact between the endogenous microflora or bacteria antigen with the epithelial cells. The mucus layer normally prevents this interaction and it is well documented that the colonic inflammation is always accompanied by a thickness and breaks in the mucus barrier. Reinforcing the mucus gel properties represents a new and potentially effective strategy to prevent bacterial adherence to the epithelial cells and mucosal tissue damage.
The viscoelastic mucus layer is formed mainly by water and mucus secreted glycoproteins or mucins that are large highly O-glycosylated proteins. These mucins form long filaments by polymerization of the subunits using their amino and carboxi-termini domains via disulfide bonds. Their central parts are made of highly repetitive sequences that are O-glycosylated and interrupted twice in the major colonic mucin MUC2, 7 times in MUC5AC and 9 times in MUC5AC by a naked domain of 110 amino acids rich in cysteine residues and named the CYS domain. This domain is conserved in evolution and was found for example in a secreted molecule of plankton made almost only of 13 CYS domains. The hydrophobic CYS domains act as crosslinkers in the gel to form aggregates between adjacent mucins. The number of CYS domains in the mucus layer likely drives the rheological properties of the gel and is responsible of the mucin networking, i.e., tight or loose net.
To test if the CYS domain plays a major function in the protection of the epithelium and may have a potential therapeutic effect in intestinal inflammation, we will generate a mouse transgenic line where the mouse tff3 promoter will drive the secretion of a string of 12 CYS domains in the colonic lumen. We will study the cytoprotective effect of the CYS domain in IBD by using a spontaneous mouse colitis model and an inducible mouse colitis model.
The ultimate goal of this project is to obtain enough data to further design a new strategy to deliver the CYS domain in the digestive tract using either living lactic acid bacteria or yeast as a new costless therapeutic strategy that will benefit IBD patients.