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.
Department of Medicine and the Center for Gastrointestinal Biology and Disease, University of North Carolina, Chapel Hill, North Carolina 27599-7080, USA.
Dirk
D
Haller
Maria P
MP
Russo
R Balfour
RB
Sartor
Christian
C
Jobin
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