IKK beta and phosphatidylinositol 3-kinase/Akt participate in non-pathogenic Gram-negative enteric bacteria-induced RelA phosphorylation and NF-kappa B activation in both primary and intestinal epithelial cell lines.
Pathogenic and enteroinvasive bacteria have been shown to trigger the I kappa B/NF-kappa B transcriptional system and proinflammatory gene expression in epithelial cells. In this study, we investigated the molecular mechanism of the commensal Gram-negative Bacteroides vulgatus-induced NF-kappa B signal transduction in intestinal epithelial cells (IEC). We report that B. vulgatus induced interleukin-1 receptor-associated kinase-1 degradation, I kappa B alpha phosphorylation/degradation, RelA and Akt phosphorylation, as well as NF-kappa B DNA binding and NF-kappa B transcriptional activity in rat non-transformed IEC-6 cells. B. vulgatus- but not interleukin-1 beta-mediated NF-kappa B transcriptional activity was inhibited by dominant negative (dn) toll-like receptor 4. Of importance, B. vulgatus induced I kappa B alpha phosphorylation/degradation and IKK alpha/beta and RelA phosphorylation in primary IEC derived from germ-free or mono-associated HLA-B27 transgenic and wild type rats, demonstrating the physiological relevance of non-pathogenic bacterial signaling in IEC. Adenoviral delivery of dn IKK beta or treatment with wortmannin inhibited B. vulgatus-induced endogenous RelA Ser-536 and GST-p65TAD (Ser-529/Ser-536) phosphorylation as well as NF-kappa B transcriptional activity in IEC-6 cells, suggesting a critical role of IKK beta and phosphatidylinositol 3-kinase/Akt in bacteria-induced RelA phosphorylation and NF-kappa B activation. Interestingly, B. vulgatus-induced I kappa B alpha degradation and NF-kappa B transcriptional activity in IEC transwell cultures were inhibited in the presence of lymphocytes. We propose that non-pathogenic B. vulgatus activates the NF-kappa B signaling pathway through both I kappa B degradation and RelA phosphorylation but that immune cells mediate tolerance of IEC to this commensal bacteria.
Haller
Dirk
D
Department of Medicine and the Center for Gastrointestinal Biology and Disease, University of North Carolina, Chapel Hill, North Carolina 27599-7080, USA.
Russo
Maria P
MP
Sartor
R Balfour
RB
Jobin
Christian
C
D000818:Animals; D030801:Animals, Genetically Modified; D001439:Bacteroides / Q000378:metabolism*; D002460:Cell Line; D051546:Cyclooxygenase 2; D004268:DNA-Binding Proteins / Q000378:metabolism; D029721:Drosophila Proteins; D004791:Enzyme Inhibitors / Q000378:metabolism; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism*; D017930:Genes, Reporter; D006801:Humans; D051550:I-kappa B Kinase; D020672:I-kappa B Proteins; D018799:Intercellular Adhesion Molecule-1 / Q000235:genetics / Q000378:metabolism; D053592:Interleukin-1 Receptor-Associated Kinases; D007413:Intestinal Mucosa / Q000166:cytology / Q000378:metabolism*; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D008070:Lipopolysaccharides / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000378:metabolism; D008565:Membrane Proteins; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010766:Phosphorylation; D011451:Prostaglandin-Endoperoxide Synthases / Q000235:genetics / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D011916:Rats, Inbred F344; D011956:Receptors, Cell Surface / Q000378:metabolism; D017472:Receptors, Interleukin-1 / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; D051996:Transcription Factor RelA
D051546:Cyclooxygenase 2; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D004791:Enzyme Inhibitors; D051550:I-kappa B Kinase; D020672:I-kappa B Proteins; D018799:Intercellular Adhesion Molecule-1; D053592:Interleukin-1 Receptor-Associated Kinases; D007527:Isoenzymes; D008070:Lipopolysaccharides; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B; D019869:Phosphatidylinositol 3-Kinases; D011451:Prostaglandin-Endoperoxide Synthases; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D011956:Receptors, Cell Surface; D017472:Receptors, Interleukin-1; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; D051996:Transcription Factor RelA; C000606204:NFKBIA protein, human; C000606206:Nfkbia protein, rat; C495345:TLR4 protein, human; C495347:Tlr4 protein, rat; C496540:PTGS2 protein, human; C494918:AKT1 protein, human; C494920:Akt1 protein, rat; C496559:CHUK protein, human; C496560:IKBKB protein, human; C496565:IKBKE protein, human