IL-10 gene-deficient mice lack TGF-beta/Smad-mediated TLR2 degradation and fail to inhibit proinflammatory gene expression in intestinal epithelial cells under conditions of chronic inflammation.
Nonpathogenic enteric bacterial species initiate and perpetuate experimental colitis in interleukin-10 geneeficient mice (IL-10(-/-)). Bacteria-specific effects on the epithelium are difficult to distinguish because of the complex nature of the gut microflora. We showed that IL-10(-/-) mice compared to wild-type mice fail to inhibit pro-inflammatory gene expression in native intestinal epithelial cells after the colonization with colitogenic Gram-positive Enterococcus faecalis. Of interest, pro-inflammatory gene expression was transient after 1 week of E. faecalis monoassociation in IECs from wild-type mice but persisted after 14 weeks of bacterial colonization in IL-10(-/-) mice. Accordingly, wild-type IECs 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 IECs at days 3, 7, 14, and 28. Consistent with the induction of TLR2-mediated RelA phosphorylation and pro-inflammatory 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(-/-) IECs. Of note, TGF-beta-activated Smad signaling was associated with the loss of TLR2 protein expression and the inhibition of NF-kappa Bependent gene expression in E. faecalis-stimulated 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 pro-inflammatory 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.
Ruiz
Pedro A
PA
Else-Kroener-Fresenius Centre for Experimental Nutritional Medicine, Technical University of Munich, 85350 Freising-Weihenstephan, Germany.
Shkoda
Anna
A
Kim
Sandra C
SC
Sartor
R Balfour
RB
Haller
Dirk
D
D000818:Animals; D004195:Disease Models, Animal; D013293:Enterococcus faecalis / Q000302:isolation & purification; D005786:Gene Expression Regulation; D007249:Inflammation / Q000235:genetics* / Q000382:microbiology; D015212:Inflammatory Bowel Diseases / Q000235:genetics / Q000382:microbiology; D016753:Interleukin-10 / Q000172:deficiency* / Q000235:genetics*; D007413:Intestinal Mucosa / Q000473:pathology / Q000503:physiopathology*; D051379:Mice; D018345:Mice, Knockout; D051195:Toll-Like Receptor 2 / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000502:physiology
C493486:Tlr2 protein, mouse; D051195:Toll-Like Receptor 2; D016212:Transforming Growth Factor beta; D016753:Interleukin-10