Antagonism of Adherent Invasive E. coli LF82 With Human α-defensin 5 in the Follicle-associated Epithelium of Patients With Ileal Crohn’s Disease

Abstract

Background The first visible signs of Crohn’s disease (CD) are microscopic erosions over the follicle-associated epithelium (FAE). The aim of the study was to investigate the effects of human α-defensin 5 (HD5) on adherent-invasive Escherichia coli LF82 translocation and HD5 secretion after LF82 exposure in an in vitro model of human FAE and in human FAE ex vivo. Methods An in vitro FAE-model was set up by the coculture of Raji B cells and Caco-2-cl1 cells. Ileal FAE from patients with CD and controls were mounted in Ussing chambers. The effect of HD5 on LF82 translocation was studied by LF82 exposure to the cells or tissues with or without incubation with HD5. The HD5 secretion was measured in human FAE exposed to LF82 or Salmonella typhimurium. The HD5 levels were evaluated by immunofluorescence, immunoblotting, and ELISA. Results There was an increased LF82 translocation across the FAE-model compared with Caco-2-cl1 (P < 0.05). Incubation of cell/tissues with HD5 before LF82 exposure reduced bacterial passage in both models. Human FAE showed increased LF82 translocation in CD compared with controls and attenuated passage after incubation with sublethal HD5 in both CD and controls (P < 0.05). LF82 exposure resulted in a lower HD5 secretion in CD FAE compared with controls (P < 0.05), whereas Salmonella exposure caused equal secretion on CD and controls. There were significantly lower HD5 levels in CD tissues compared with controls. Conclusions Sublethal HD5 reduces the ability of LF82 to translocate through FAE. The HD5 is secreted less in CD in response to LF82, despite a normal response to Salmonella. This further implicates the integrated role of antimicrobial factors and barrier function in CD pathogenesis.

Role of adherent invasive Escherichia coli in pathogenesis of inflammatory bowel disease

“…Vitamin D3-deficient mice treated with DSS showed significant epithelial dysfunction and increased colitis susceptibility, aggravating the damage caused by AIEC colonization. Thus, vitamin D deficiency after AIEC infection may disrupt the mucosal barrier, leading to increased susceptibility to mucosal damage and an increased risk of IBD[ 111 ].…”

Effects of fecal stream deprivation on human intestinal barrier after loop ileostomy

“…33 In the human gut, α-defensin proteins, including α-defensin 5 and α-defensin 6, are the most abundant, diverse, and highly expressed antimicrobial proteins. 34 Previous studies have shown that α-defensin has spectral bactericidal activity against gram-positive and gram-negative bacteria and, in some instances, against fungi, viruses, and protozoa. 35 However, few studies have focused on the exact impact of fecal stream deprivation on the secretion of antimicrobial peptides in the small intestine.…”

“…Evidence has recently emerged indicating that antimicrobial peptides secreted by Paneth cells have vital roles in innate enteric immunity and in the regulation of intestinal microbiota 33 . In the human gut, α‐defensin proteins, including α‐defensin 5 and α‐defensin 6, are the most abundant, diverse, and highly expressed antimicrobial proteins 34 . Previous studies have shown that α‐defensin has spectral bactericidal activity against gram‐positive and gram‐negative bacteria and, in some instances, against fungi, viruses, and protozoa 35 .…”