Abstract
Ileal lesions in Crohn's disease patients are colonized by pathogenic adherent-invasive Escherichia coli (AIEC) that harbor various virulence factors involved in adhesion to and invasion of intestinal epithelial cultured cells. We investigated in a mouse model of colonic inflammation the behavior of virulent AIEC reference bacteria LF82 compared to that of nonflagellated LF82 mutants. BALBc/J mice with intact or dextran sulfate sodium (DSS)-injured colon were orally challenged daily with 10(8) bacteria. The severity of colitis was assessed by determining disease activity index, colonic histological score, and myeoloperoxidase activity. Flagellin receptor and cytokine expression was measured by reverse-transcriptase polymerase chain reaction (RT-PCR) in colonic tissue. In contrast to nonpathogenic E. coli, virulent LF82 bacteria exacerbated colitis in DSS-treated mice, substantially reducing survival rate, greatly lowering stool consistency, inducing marked weight loss and increased rectal bleeding, and significantly increasing erosive lesions and mucosal inflammation. Nonflagellated LF82 mutants behaved like nonpathogenic E. coli K-12. Interestingly, oral infection with LF82 virulent bacteria, but not with a nonvirulent LF82 mutant, induced a 7.0-fold increase in the levels of TLR5 and a 3.1-fold increase in those of ipaf mRNA, which encode respectively membrane and cytosolic receptors involved in the recognition of flagellin. Hence, a 5.6-fold increase in IL-1beta and a 5.3-fold increase in mRNA of IL-6 were observed in mice challenged with AIEC LF82 bacteria. Crohn's disease-associated virulent AIEC LF82 bacteria, via expression of flagella, are able to potentiate an inflammatory mucosal immune response involving increased expression of TLR5 and IPAF flagellin receptors.
Highlights
MethodsBALBc/J mice with intact or dextran sulfate sodium (DSS)-injured colon were orally challenged daily with 108 bacteria
Ileal lesions in Crohn’s disease patients are colonized by pathogenic adherent-invasive Escherichia coli (AIEC) that harbor various virulence factors involved in adhesion to and invasion of intestinal epithelial cultured cells
In Crohn’s disease (CD) the ileal mucosa of patients is abnormally colonized by pathogenic E. coli able to adhere to and to invade intestinal epithelial cells, termed adherent-invasive E. coli (AIEC).[7]
Summary
BALBc/J mice with intact or dextran sulfate sodium (DSS)-injured colon were orally challenged daily with 108 bacteria. Escherichia coli Challenge in Injured Colon Mouse Model Six-week-old BALBc/J male mice (Ϸ22 g) were purchased from the Charles River Laboratory (L’arbresle, France) They received 2% (w/v) DSS (MW ϭ 36,000 –50,000, MP Biomedicals, Solon, OH) in drinking water for 14 days to induce colon injury, and were orally challenged daily by 108 bacteria in CMC during the same period. AIEC LF82 infection strongly enhanced TLR5 and ipaf mRNA levels (7.0-fold and 3.1-fold, respectively) compared with those in noninfected mice (Fig. 5E,F) This was not observed in mice infected with nonflagellated mutant LF82-⌬fliC, and restoration of flagella expression by transcomplementation of LF82-⌬fliC mutant with cloned fliC led to similar higher mRNA levels of both TLR5 and IPAF receptors (5.4-fold and 3.0-fold, respectively) than those observed for wildtype LF82 bacteria. This indicates that expression of flagella in AIEC LF82 bacteria can increase the expression of TLR5 and IPAF flagellin receptors
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
