Abstract
In Crohn’s disease (CD) patients, the adherent-invasive Escherichia coli (AIEC) pathovar contributes to the chronic inflammation typical of the disease via its ability to invade gut epithelial cells and to survive in macrophages. We show that, in the AIEC strain LF82, inactivation of the pyrD gene, encoding dihydroorotate dehydrogenase (DHOD), an enzyme of the de novo pyrimidine biosynthetic pathway, completely abolished its ability of to grow in a macrophage environment-mimicking culture medium. In addition, pyrD inactivation reduced flagellar motility and strongly affected biofilm formation by downregulating transcription of both type 1 fimbriae and curli subunit genes. Thus, the pyrD gene appears to be essential for several cellular processes involved in AIEC virulence. Interestingly, vidofludimus (VF), a DHOD inhibitor, has been proposed as an effective drug in CD treatment. Despite displaying a potentially similar binding mode for both human and E. coli DHOD in computational molecular docking experiments, VF showed no activity on either growth or virulence-related processes in LF82. Altogether, our results suggest that the crucial role played by the pyrD gene in AIEC virulence, and the presence of structural differences between E. coli and human DHOD allowing for the design of specific inhibitors, make E. coli DHOD a promising target for therapeutical strategies aiming at counteracting chronic inflammation in CD by acting selectively on its bacterial triggers.
Highlights
In Crohn’s disease (CD) patients, the adherent-invasive Escherichia coli (AIEC) pathovar contributes to the chronic inflammation typical of the disease via its ability to invade gut epithelial cells and to survive in macrophages
We have performed an in vitro study comparing the immunomodulatory effects of Lactobacilli and Bifidobacteria probiotic strains, showing that production of pro-inflammatory cytokines and the activation of the IL-23/Th17 axis in response to AIEC is effectively counteracted by probiotics in cells from healthy subjects and from individuals suffering with ulcerative colitis, but not in cells from CD patients [30], suggesting that probiotics might have a limited impact in CD
In order to identify genes that might be involved in AIEC virulence, we created a transposon mutagenesis library in the LF82 strain, using the EZ-Tn5
Summary
Crohn’s disease (CD) is characterized by chronic intestinal inflammation resulting from inappropriate and persistent activation of the intestinal mucosal immune system [1]. We have performed an in vitro study comparing the immunomodulatory effects of Lactobacilli and Bifidobacteria probiotic strains, showing that production of pro-inflammatory cytokines and the activation of the IL-23/Th17 axis in response to AIEC is effectively counteracted by probiotics in cells from healthy subjects and from individuals suffering with ulcerative colitis, but not in cells from CD patients [30], suggesting that probiotics might have a limited impact in CD. In this manuscript, we report that a mutation inactivating the pyrD gene of the AIEC. Based on the observation that E. coli DHOD differs from the human enzyme, and has a low sequence identity to DHOD from probiotic species like Lactococcus lactis, we propose that the development of specific inhibitors of E. coli DHOD might be a potentially interesting therapeutic strategy for CD remission via selective inhibition of AIEC growth and virulence
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