Cross-talk among Toll-like receptors and their ligands.
Toll-like receptors (TLRs) 4, 5, 7 and 9 belong to a family of proteins that recognize mainly conserved microbial motifs. Though each TLR has a highly specific ability to recognize a particular microbial pattern, recent papers suggest that some ligands are able to affect the expression of different TLRs. In this paper, we have investigated TLR4, 5, 7 and 9 expression, both at mRNA and protein level, following treatment of different intestinal epithelial cell lines with LPS, flagellin, loxiribine, CpG-oligodeoxynucleotide and peptidoglycan, to assess if the different TLR ligands may modulate the expression of the respective TLR and of the unrelated ones. Our results show that a cross-talk exists between TLRs and various ligands, indicating a cross-regulation among these pattern recognition receptors. In particular, TLR4 was generally down-regulated by treatment with ligands other than LPS, while flagellin and unrelated microbial-associated molecular patterns exerted a general stimulatory activity as regards TLR5 expression. Concerning TLR7 and 9, we have observed a more variable behaviour of the various cell lines with the different ligands. Together, our results demonstrate that the expression of TLRs in intestinal cells is highly dynamic and tightly regulated in response to encountered microbial stimuli.
Palazzo
Marco
M
Department of Human Morphology, Pathology, Università degli Studi di Milano, 20133Milan, Italy.
Gariboldi
Silvia
S
Zanobbio
Laura
L
Dusio
Giuseppina F
GF
Selleri
Silvia
S
Bedoni
Marzia
M
Balsari
Andrea
A
Rumio
Cristiano
C
D000818:Animals; D000942:Antigens, Bacterial / Q000276:immunology* / Q000378:metabolism; D045744:Cell Line, Tumor; D004847:Epithelial Cells / Q000276:immunology / Q000378:metabolism; D019073:HT29 Cells; D006801:Humans; D016209:Interleukin-8 / Q000096:biosynthesis / Q000276:immunology*; D008024:Ligands; D008264:Macrophages / Q000276:immunology / Q000378:metabolism; D051379:Mice; D009838:Oligodeoxyribonucleotides / Q000276:immunology / Q000378:metabolism; D010457:Peptidoglycan / Q000276:immunology / Q000378:metabolism; D020239:Receptor Cross-Talk; D051193:Toll-Like Receptors / Q000276:immunology / Q000378:metabolism*
D000942:Antigens, Bacterial; C408982:CPG-oligonucleotide; D016209:Interleukin-8; D008024:Ligands; D009838:Oligodeoxyribonucleotides; D010457:Peptidoglycan; D051193:Toll-Like Receptors