title: IL-10 gene-deficient mice lack TGF-beta/Smad signaling and fail to inhibit proinflammatory gene expression in intestinal epithelial cells after the colonization with colitogenic Enterococcus faecalis.
abstract: Nonpathogenic enteric bacterial species initiate and perpetuate experimental colitis in IL-10 gene-deficient mice (IL-10(-/-)). Bacteria-specific effects on the epithelium are difficult to dissect due to the complex nature of the gut microflora. We showed that IL-10(-/-) mice compared with wild-type mice fail to inhibit proinflammatory gene expression in native intestinal epithelial cells (IEC) after the colonization with colitogenic Gram-positive Enterococcus faecalis. Interestingly, proinflammatory gene expression was transient after 1 wk of E. faecalis monoassociation in IEC from wild-type mice, but persisted after 14 wk of bacterial colonization in IL-10(-/-) mice. Accordingly, wild-type IEC expressed phosphorylated NF-kappaB subunit RelA (p65) and phosphorylated Smad2 only at day 7 after bacterial colonization, whereas E. faecalis-monoassociated IL-10(-/-) mice triggered persistent RelA, but no Smad2 phosphorylation in IEC at days 3, 7, 14, and 28. Consistent with the induction of TLR2-mediated RelA phosphorylation and proinflammatory gene expression in E. faecalis-stimulated cell lines, TLR2 protein expression was absent after day 7 from E. faecalis-monoassociated wild-type mice, but persisted in IL-10(-/-) IEC. Of note, TGF-beta1-activated Smad signaling was associated with the loss of TLR2 protein expression and the inhibition of NF-kappaB-dependent gene expression in IEC lines. In conclusion, E. faecalis-monoassociated IL-10(-/-), but not wild-type mice lack protective TGF-beta/Smad signaling and fail to inhibit TLR2-mediated proinflammatory gene expression in the intestinal epithelium, suggesting a critical role for IL-10 and TGF-beta in maintaining normal epithelial cell homeostasis in the interplay with commensal enteric bacteria.
authors.affiliation: Centre for Nutrition and Food Research, Immunobiology of Nutrition, Technical University of Munich, Freising-Weihenstephan, Germany.
authors.forename: Pedro A
authors.initials: PA
authors.lastname: Ruiz
authors.forename: Anna
authors.initials: A
authors.lastname: Shkoda
authors.forename: Sandra C
authors.initials: SC
authors.lastname: Kim
authors.forename: R Balfour
authors.initials: RB
authors.lastname: Sartor
authors.forename: Dirk
authors.initials: D
authors.lastname: Haller
mesh_terms: D000818:Animals; D002460:Cell Line; D002478:Cells, Cultured; D003092:Colitis / Q000235:genetics* / Q000276:immunology / Q000382:microbiology; D004268:DNA-Binding Proteins / Q000172:deficiency / Q000502:physiology; D013293:Enterococcus faecalis / Q000254:growth & development / Q000276:immunology; D005786:Gene Expression Regulation / Q000235:genetics / Q000276:immunology; D016908:Gram-Positive Bacterial Infections / Q000235:genetics / Q000276:immunology; D018836:Inflammation Mediators / Q000037:antagonists & inhibitors* / Q000378:metabolism; D016753:Interleukin-10 / Q000096:biosynthesis / Q000172:deficiency* / Q000235:genetics; D007413:Intestinal Mucosa / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D051379:Mice; D008809:Mice, Inbred C3H; D018345:Mice, Knockout; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology; D010766:Phosphorylation; D011956:Receptors, Cell Surface / Q000096:biosynthesis / Q000172:deficiency / Q000502:physiology; D015398:Signal Transduction / Q000235:genetics* / Q000276:immunology; D051785:Smad Proteins; D051195:Toll-Like Receptor 2; D015534:Trans-Activators / Q000172:deficiency / Q000502:physiology; D051996:Transcription Factor RelA; D016212:Transforming Growth Factor beta / Q000172:deficiency / Q000502:physiology; D053773:Transforming Growth Factor beta1
chemical_list: D004268:DNA-Binding Proteins; D018836:Inflammation Mediators; D016328:NF-kappa B; D011956:Receptors, Cell Surface; D051785:Smad Proteins; C508961:Tgfb1 protein, mouse; C493486:Tlr2 protein, mouse; D051195:Toll-Like Receptor 2; D015534:Trans-Activators; D051996:Transcription Factor RelA; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D016753:Interleukin-10