scholarly journals TRIF Mediates Toll-like Receptor 5-induced Signaling in Intestinal Epithelial Cells

2010 ◽  
Vol 285 (48) ◽  
pp. 37570-37578 ◽  
Author(s):  
Yoon Jeong Choi ◽  
Eunok Im ◽  
Hyo Kyun Chung ◽  
Charalabos Pothoulakis ◽  
Sang Hoon Rhee
Keyword(s):  
Epithelial Cells ◽  
Intestinal Epithelial Cells ◽  
Intestinal Epithelial ◽  
Toll Like Receptor ◽  
Toll Like Receptor 5

Flagellin-induced tolerance of the Toll-like receptor 5 signaling pathway in polarized intestinal epithelial cells

2007 ◽  
Vol 292 (3) ◽  
pp. G767-G778 ◽  
Author(s):  
Jun Sun ◽  
Pamela E. Fegan ◽  
Anjali S. Desai ◽  
James L. Madara ◽  
Michael E. Hobert
Keyword(s):  
Epithelial Cells ◽  
Intestinal Epithelial Cells ◽  
Prior Exposure ◽  
Intestinal Epithelial ◽  
Toll Like Receptor ◽  
Proinflammatory Response ◽  
Gram Negative ◽  
Human Intestinal Epithelial Cells ◽  
Induced Tolerance ◽  
Toll Like Receptor 5

Salmonella typhimurium is a gram-negative enteric pathogen that invades the mucosal epithelium and is associated with diarrheal illness in humans. Flagellin from S. typhimurium and other gram-negative bacteria has been shown to be the predominant proinflammatory mediator through activation of the basolateral Toll-like receptor 5 (TLR5). Recent evidence has shown that prior exposure can render immune cells tolerant to subsequent challenges by TLR ligands. Accordingly, we examined whether prior exposure to purified flagellin would render human intestinal epithelial cells insensitive to future contact. We found that flagellin-induced tolerance is common to polarized epithelial cells and prevents further activation of proinflammatory signaling cascades by both purified flagellin and Salmonella bacteria but does not affect TNF-α stimulation of the same pathways. Flagellin tolerance is a rapid process that does not require protein synthesis, and that occurs within 1 to 2 h of flagellin exposure. Prolonged flagellin exposure blocks activation of the NF-κB, MAPK, and phosphoinositol 3-kinase signaling pathways and results in the internalization of a fraction of the basolateral TLR5 without affecting the polarity or total expression of TLR5. After removal of flagellin, cells require more than 24 h to fully recover their ability to mount a normal proinflammatory response. We have found that activation of phosphoinositol 3-kinase and Akt by flagellin has a small damping effect in the early stages of flagellin signaling but is not responsible for tolerance. Our study indicates that inhibition of TLR5-associated IL-1 receptor-associated kinase-4 activity occurs during the development of flagellin tolerance and is likely to be the cause of tolerance.

scholarly journals Vibrio cholerae Flagellins Induce Toll-Like Receptor 5-Mediated Interleukin-8 Production through Mitogen-Activated Protein Kinase and NF-κB Activation

2008 ◽  
Vol 76 (12) ◽  
pp. 5524-5534 ◽  
Author(s):  
Lisa M. Harrison ◽  
Prasad Rallabhandi ◽  
Jane Michalski ◽  
Xin Zhou ◽  
Susan R. Steyert ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Epithelial Cells ◽  
Intestinal Epithelial Cells ◽  
Mitogen Activated Protein Kinase ◽  
Intestinal Epithelial ◽  
Toll Like Receptor ◽  
T84 Cells ◽  
Mitogen Activated Protein ◽  
Toll Like Receptor 5 ◽  
Culture Supernatants

ABSTRACT Vaccine reactogenicity has complicated the development of safe and effective live, oral cholera vaccines. Δctx Vibrio cholerae mutants have been shown to induce inflammatory diarrhea in volunteers and interleukin-8 (IL-8) production in cultured intestinal epithelial cells. Bacterial flagellins are known to induce IL-8 production through Toll-like receptor 5 (TLR5). Since the V. cholerae genome encodes five distinct flagellin proteins, FlaA to FlaE, with homology to conserved TLR5 recognition regions of Salmonella FliC, we hypothesized that V. cholerae flagellins may contribute to IL-8 induction through TLR5 and mitogen-activated protein kinase (MAPK) signaling. Each purified recombinant V. cholerae flagellin induced IL-8 production in T84 intestinal epithelial cells and also induced nuclear factor kappa B (NF-κB) activation in HEK293T/TLR5 transfectants, which was blocked by cotransfection with a TLR5 dominant-negative construct, demonstrating TLR5 specificity. Supernatants derived from ΔflaAC and ΔflaEDB mutants induced IL-8 production in HT-29 intestinal epithelial cells and in HEK293T cells overexpressing TLR5, whereas ΔflaABCDE supernatants induced significantly less IL-8 production, demonstrating the contribution of multiple flagellins in IL-8 induction. NF-κB activation by ΔflaABCDE supernatants was partially restored by flaA or flaAC complementation. Western analysis confirmed the presence of V. cholerae flagellins in culture supernatants. Purified recombinant V. cholerae FlaA activated the MAPKs p38, c-jun N-terminal kinase (JNK), and extracellular regulated kinase (ERK) in T84 cells. FlaA-induced IL-8 production in T84 cells was inhibited by the p38 inhibitor in combination with either the JNK or ERK inhibitors. Collectively, these data suggest that V. cholerae flagellins are present in culture supernatants and can induce TLR5- and MAPK-dependent IL-8 secretion in host cells.

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