Ligand-induced differential cross-regulation of Toll-like receptors 2, 4 and 5 in intestinal epithelial cells.
Toll-like receptors (TLR) 2, TLR4 and TLR5 are primary mucosal sensors of microbial patterns. Dissection of the cross-talk between TLRs in intestinal cells has thus far been hampered by the lack of functional TLR2 and TLR4 in in vitro model systems. Here we report that the mouse intestinal epithelial cell line mIC(cl2) expresses these TLRs and that receptor expression and function are regulated by environmental TLR stimuli. Our results show that stimulation of TLR5 by bacterial flagellin resulted in upregulated TLR2 and TLR4 mRNA and concomitant sensitization of the cells for subsequent TLR2 (Pam(3)CSK(4)) and TLR4 (LPS) stimulation. Exposure to low amounts of either Pam(3)CSK(4) or LPS in turn downregulated TLR5 mRNA and attenuated subsequent flagellin-mediated NF-kappaB activation, pointing to a negative feedback mechanism. Pam(3)CSK(4) and LPS also downregulated TLR4 mRNA but upregulated TLR2 mRNA and sensitized cells for subsequent TLR2 stimulation. Inhibition of the phosphatidyl-inositol-3-kinase/Akt pathway only affected LPS-mediated TLR cross-talk indicating that differential TLR cross-regulation was conferred via different mechanisms. Together, our results demonstrate that the expression and function of TLR in intestinal cells are highly dynamic and tightly regulated in response to encountered bacterial stimuli.
van Aubel
Rémon A M H
RA
Department of Infectious Diseases and Immunology, Utrecht University, Yalelaan 1, 3584 CL Utrecht, The Netherlands.
Keestra
A Marijke
AM
Krooshoop
Daniëlle J E B
DJ
van Eden
Willem
W
van Putten
Jos P M
JP
D000818:Animals; D002460:Cell Line; D004847:Epithelial Cells / Q000187:drug effects* / Q000378:metabolism; D005408:Flagellin / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects; D006367:HeLa Cells; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000166:cytology* / Q000187:drug effects; D008024:Ligands; D055666:Lipopeptides; D008070:Lipopolysaccharides / Q000494:pharmacology*; D051379:Mice; D018448:Models, Immunological; D010455:Peptides / Q000494:pharmacology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020239:Receptor Cross-Talk / Q000187:drug effects*; D051195:Toll-Like Receptor 2 / Q000819:agonists / Q000235:genetics / Q000378:metabolism; D051197:Toll-Like Receptor 4 / Q000819:agonists / Q000235:genetics / Q000378:metabolism; D051198:Toll-Like Receptor 5 / Q000819:agonists / Q000235:genetics / Q000378:metabolism; D051193:Toll-Like Receptors / Q000819:agonists / Q000235:genetics / Q000378:metabolism*
D008024:Ligands; D055666:Lipopeptides; D008070:Lipopolysaccharides; C508075:Pam(3)CSK(4) peptide; D010455:Peptides; D012333:RNA, Messenger; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D051198:Toll-Like Receptor 5; D051193:Toll-Like Receptors; D005408:Flagellin; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt