Intestinal Persistence of Crohnʼs Disease-associated Adherent-Invasive Escherichia Coli Enhances Spontaneous Visceral Hypersensitivity

Abstract

Crohn's disease (CD) results from breakdown of homeostasis between intestinal microbiota and the mucosal immune system, with both genetic and environmental influencing factors. Various studies in CD patients have reported abnormal gut colonization by pathogenic Escherichia coli referred to as adherent invasive E. coli (AIEC) linked to overexpression of the bacterial colonizing receptor CEACAM6. Among characteristics of CD are the presence of colonic hypersensitivity and abdominal pain. The aim of our study was to investigate whether, intestinal AIEC colonization could be at the origin of spontaneous development of visceral hypersensitivity and whether this latter may persist even after bacterial clearance and intestinal inflammation alleviation. Transgenic mice overexpressing the human CEACAM6 glycoprotein and their wild-type littermates were orally infected by CD-associated AIEC bacteria (reference strain LF82) or by a non-pathogenic E. coli (MG1655). At 3, 9 and 21 days after infection, visceral hypersensitivity was assessed using a technique based on measuring electromyographic abdominal contractions induced by colorectal distension. Briefly, by progressive inflation of a balloon inserted into the colon, stomach cramps whose amplitude is proportional to the colon sensitivity were induced. Inflammation was monitored using anatomical indicators of colitis such as spleen and colon weight, and assessed by determination of the colonic myeloperoxidase (MPO) activity and expression of systemic pro-inflammatory cytokines. Human CEACAM6 expression in transgenic mice induced a significant decrease in the visceral hypersensitivity in comparison to their housekeeping WT mice. Otherwise, infection with CD-associated AIEC LF82, but not with non-pathogenic E. coli MG1655, highly increased levels of visceral hypersensitivity at day 3 post-infection in comparison to their housekeeping WT. Of interest, such visceral hypersensitivity persisted in transgenic mice after bacterial clearance and did not match with intestinal inflammation. In the present study, we show a direct involvement of CD-associated AIEC LF82 colonization in colonic hypersensitivity. This was observed only in transgenic mice expressing CEACAM6, indicating that increased AIEC intestinal persistence may impact on colonic sensitivity, which persists after bacterial clearance. Thus hypersensitivity and abdominal pain in CD patients could be linked to bacterial infection.