Transforming growth factor-beta 1 inhibits non-pathogenic Gram negative bacteria-induced NF-kappa B recruitment to the interleukin-6 gene promoter in intestinal epithelial cells through modulation of histone acetylation.
We have shown that non-pathogenic enteric Gram-negative Bacteroides vulgatus induces RelA phosphorylation, NF-kappaB activation, and proinflammatory gene expression in primary and intestinal epithelial cell (IEC) lines. We now demonstrate the transient induction of nuclear phospho-RelA (day 3) followed by persistent activation of phospho-Smad2 (days 3 and 7) in IEC from mucosal tissue sections of B. vulgatus-monoassociated rats, indicating that both NF-kappaB and transforming growth factor-beta1 (TGF-beta1) signaling are induced in vivo following bacterial colonization. Interestingly, TGF-beta1 inhibited B. vulgatus- and lipopolysaccharide (LPS)-induced NF-kappaB transcriptional activity as well as interleukin-6 (IL-6) mRNA accumulation and protein secretion in IEC. The inhibitory effect of TGF-beta1 is mediated independently of B. vulgatus/LPS-induced IkappaBalpha, Akt, and RelA phosphorylation as well as NF-kappaB DNA binding activity. Moreover, the specific histone deacetylase inhibitor trichostatin A blocked B. vulgatus/LPS-induced histone acetylation/phosphorylation (Lys-9/Ser-10) and reversed TGF-beta1-mediated inhibition of IL-6 gene expression. Chromatin immunoprecipitation analysis revealed that B. vulgatus/LPS-induced RelA recruitment to the IL-6 promoter is inhibited by TGF-beta1 treatment. Adenoviral delivery of Smad7 and dominant negative Smad3 (SmadDelta3) reversed the TGF-beta1-mediated inhibition of NF-kappaB transcriptional activity and NF-kappaB recruitment to the IL-6 promoter. In addition, TGF-beta1 and Ad5Smad3/4 prevent B. vulgatus/LPS-induced CBP/p300 and p65 nuclear co-association. We concluded that the TGF-beta1/Smad signaling pathway helps maintain normal intestinal homeostasis to commensal luminal enteric bacteria by regulating NF-kappaB signaling in IEC through altered histone acetylation.
Haller
Dirk
D
Department of Medicine, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
Holt
Lisa
L
Kim
Sandra C
SC
Schwabe
Robert F
RF
Sartor
R Balfour
RB
Jobin
Christian
C
D000107:Acetylation; D000818:Animals; D001439:Bacteroides / Q000187:drug effects / Q000502:physiology*; D001442:Bacteroides Infections / Q000378:metabolism; D002460:Cell Line; D006090:Gram-Negative Bacteria / Q000187:drug effects / Q000502:physiology; D006657:Histones / Q000378:metabolism*; D015850:Interleukin-6 / Q000235:genetics*; D007413:Intestinal Mucosa / Q000166:cytology*; D008070:Lipopolysaccharides / Q000494:pharmacology; D051379:Mice; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D051381:Rats; D011916:Rats, Inbred F344; D015398:Signal Transduction / Q000187:drug effects; D014158:Transcription, Genetic / Q000187:drug effects; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D053773:Transforming Growth Factor beta1
D006657:Histones; D015850:Interleukin-6; D008070:Lipopolysaccharides; D016328:NF-kappa B; C508961:Tgfb1 protein, mouse; C508962:Tgfb1 protein, rat; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1