Final Report Summary - MIRNA-AIEC (Role of microRNAs in host responses to Crohn's disease-associated adherent-invasive Escherichia coli) Inflammatory bowel diseases (IBD), including Crohn's disease (CD) and ulcerative colitis (UC), are thought to result from an inappropriate inflammatory response to normal components of the intestinal microbiota in genetically susceptible individuals. Alterations in the composition of the microbiota have been associated with IBD, particularly a high prevalence of adherent-invasive E. coli (AIEC). The host research group has phenotypically characterized the AIEC strains, and shown that they are able to: adhere to and invade human intestinal epithelial cells (IECs); up-regulate the adhesion molecule CEACAM6, which acts as a host epithelial receptor for AIEC; survive and replicate within macrophages; induce pro-inflammatory cytokine production; and exacerbate intestinal inflammation in a transgenic mouse model expressing CEACAM receptors. It is recently shown that AIEC are subject to autophagic control within host cells, and that a functional autophagy is required to restrain the replication of AIEC. So far, the factors or the molecular mechanisms underlying the control of AIEC intracellular invasion by autophagy have yet to be identified.Recent studies have shown dysregulation of microRNAs (miRNAs), a new key group of gene regulators, in the mucosa of CD patients, suggesting a role for miRNAs as contributors to IBD susceptibility. The goal of this project is to determine the miRNAs dysregulated in host cells upon infection with AIEC, and the mechanisms through which they contribute to host responses. This was achieved via three main objectives:Objective 1: To determine the potential role and mechanism by which miRNAs modulate the host responses of intestinal epithelial cells to adherent-invasive E. coli.Objective 2: To study the regulation of CEACAM6 by miRNAs in intestinal epithelial cells during pathophysiological states, and in host responses to AIEC infection.Objective 3: To test the hypothesis that AIEC impair autophagy to replicate in host cells by modulating expression of host miRNAs.During the period of this project, we were able to identify 12 miRNAs that are deregulated in intestinal epithelial Caco2 cells in response to infection with the AIEC reference strain LF82. Functional analysis revealed that several dysregulated miRNAs are involved in host autophagy response to AIEC infection by regulating expression of autophagy-related genes. Interestingly, inhibition of these miRNAs in cultured IECs blocked AIEC-induced inhibition of autophagy expression and restored functional autophagy. This resulted in more-effective clearance of intracellular AIEC and reduced AIEC-induced inflammation. This suggests that AIEC infection suppresses autophagy response to replicate within host cells by dysregulating miRNA expression. We also explored the mechanism underlying regulation of CEACAM6 expression under physiological and pathological conditions via miRNAs. Overexpression of CEACAM6-targeting miRNAs in IECs impaired adhesion and invasion of AIEC and subsequently decreased AIEC-induced inflammation. MiRNAs are therefore promising therapeutic targets to inhibit the intracellular replication of CD-associated pathogenic bacteria and bacteria-induced inflammation.These results were presented at several national and international conferences, as well as published in peer-reviewed journals, such as Gastroenterology-the top journal in the field of Gastroenterology.In summary, the results achieved from this project shed light on the mechanism by which miRNAs are involved in host responses to AIEC infection, which could help to identify new biomarkers and potential miRNA-based therapeutic targets for Crohn’s disease that would benefit the community at large. Therefore, this project is in line with the efforts that Europe is putting in developing therapeutics for treatment of intestinal disorders. The collaborative experiments proposed in this project, which include a number of research associates with expertise in microbiology, molecular biology and cellular biology were synergized to allow rapid development of new approaches for the study of IBD. Besides the outcome of the project regarding results and publications, both sides, me and the host research group, have learned and benefited from the others expertise. Thus, this project contributed undoubtedly to increase EU scientific excellence and therefore the competitiveness of Europe for researchers.
