Invading bacteria are recognized, captured and killed by a specialized form of autophagy, called xenophagy. Recently, defects in xenophagy in Crohn’s disease (CD) have been implicated in the pathogenesis of human chronic inflammatory diseases of uncertain etiology of the gastrointestinal tract. We show here that pathogenic adherent-invasive Escherichia coli (AIEC) isolated from CD patients are able to adhere and invade neutrophils, which represent the first line of defense against bacteria. Of particular interest, AIEC infection of neutrophil-like PLB-985 cells blocked autophagy at the autolysosomal step, which allowed intracellular survival of bacteria and exacerbated interleukin-8 (IL-8) production. Interestingly, this block in autophagy correlated with the induction of autophagic cell death. Likewise, stimulation of autophagy by nutrient starvation or rapamycin treatment reduced intracellular AIEC survival and IL-8 production. Finally, treatment with an inhibitor of autophagy decreased cell death of AIEC-infected neutrophil-like PLB-985 cells. In conclusion, excessive autophagy in AIEC infection triggered cell death of neutrophils.

Crohn disease (CD) ileal lesions are colonized by adherent-invasive E. coli (AIEC) that locally induce inflammation. Hypoxia inducible factor (HIF)-1alpha protein is expressed in acute and chronically inflamed site; however the molecular basis of this expression is not fully understood. The aim of the study was to access whether AIEC induce HIF-1α expression and to study the consequence of HIF-1α expression on the onset of Crohn disease pathogenesis. We show that HIF-1α is maximally expressed in inflamed ileal epithelium of CD-patients. CEACAM6, a protein that acts as a receptor of AIEC, is expressed in this particular condition. Using CEABAC 10 transgenic mice that express CEACAM6, we show that AIEC bacteria, but not non-pathogenic E. coli K12, induce the production of HIF-1alpha protein and the activation of VEGF/VEGFR signaling. Downstream analyses on human intestinal epithelial cells silenced for hif- 1α, highlight the crucial role of this protein in production of pro-angiogenic factors. This study highlights the crucial role of AIEC bacteria as promoter of inflammatory disorders of the gastrointestinal tract and provides clear evidence that HIF-1α protein plays a major role in mediating this effect.