P009 Autophagy-related host factors are implicated in the incapability of macrophages from Crohn’s disease patients to mediate adherent-invasive E. coli clearance

Abstract

Several experimental data have highlighted the potential role of intestinal macrophages in the pathogenesis of Crohn’s disease (CD). These macrophages present a defect in the control of CD-associated adherent-invasive E. coli (AIEC) replication, which could be linked to altered autophagy. We investigated the impact of several CD-associated singer nucleotide polymorphisms (SNPs) including those implicated in autophagy on the ability of macrophages from CD patients to mediate AIEC bacterial clearance. Peripheral blood monocyte-derived macrophages (MDM) were obtained from 95 CD patients, 30 ulcerative colitis (UC) patients and 15 healthy subjects genotyped for CD-associated SNPs-related to autophagy, especially IRGM (rs10065172) and ULK1 (rs12303764) and, infected with AIEC LF82 reference strain. Functional assay were performed on MDM after AIEC infection and/or after a short-term silencing of ULK1 gene. The numbers of intracellular bacteria were determined using gentamicin protection assay. IRGM, ULK1 and p62 protein expression was determined by western blot. AIEC survival was increased within MDM from CD patients compared with those from UC patients or healthy subjects (p = 0.0019). MDM from CD patients failed to mediate AIEC bacterial clearance especially in patients harbouring the CD-associated IRGM SNP (p = 0.045). In contrast, AIEC survival was decreased in MDM from patients with the CD-associated ULK1 SNP (p = 0.046). Expression of ULK1, but not IRGM and p62, was increased in MDM from CD patients infected by AIEC bacteria compared with MDM from UC patients or healthy subjects (p = 0.0056) and are significantly correlated with the AIEC survival (p = 0.0369). In the same way, the down-regulation of ULK1 within MDM limits the AIEC survival (p = 0.0018) within MDM and could regulate the autophagic flux suggested by an increase of the expression of p62 (p = 0.0043). We confirmed that MDM from CD patients failed to mediate AIEC bacterial clearance compared with those of UC or healthy subjects. Our results highlight a role of CD-associated SNPs, related to autophagy, IRGM and ULK1, on the ability of macrophages from CD patients to mediate AIEC bacterial clearance. At the protein level, our data suggested a potential role of the protein ULK1, the cornerstone of autophagy initiation, to control AIEC bacteria in patients with CD. This protein could be a potential target to alter the interaction between macrophages and AIEC in patients with CD.