Toll-like receptor 4 mediates induction of the Bcl10-NFkappaB-interleukin-8 inflammatory pathway by carrageenan in human intestinal epithelial cells.
The sulfated polysaccharide carrageenan (CGN) induces activation of NFkappaB and interleukin 8 (IL-8) in human colonic epithelial cells through a pathway of innate immunity mediated by Bcl10 (B-cell CLL/lymphoma 10). In this report, we identify Toll-like receptor 4 (TLR4), a member of the family of innate immune receptors, as the surface membrane receptor for CGN in human colonic epithelial cells. Experiments with fluorescence-tagged CGN demonstrated a marked reduction in binding of CGN to human intestinal epithelial cells and to RAW 264.7 mouse macrophages, following exposure to TLR4 blocking antibody (HTA-125). Binding of CGN to 10ScNCr/23 mouse macrophages, which are deficient in the genetic locus for TLR4, was absent. Additional experiments with TLR4 blocking antibody and TLR4 small interfering RNAs showed 80% reductions in CGN-induced increases in Bcl10 and IL-8. Transfection with dominant-negative MyD88 plasmid demonstrated MyD88 dependence of the CGN-TLR4-triggered increases in Bcl10 and IL-8. Therefore, these results indicate that CGN-induced inflammation in human colonocytes proceeds through a pathway of innate immunity, perhaps related to the unusual alpha-1,3-galactosidic linkage characteristic of CGN, and suggest how dietary CGN intake may contribute to human intestinal inflammation. Because CGN is a commonly used food additive in the Western diet, clarification of its effects and mechanisms of action are vital to issues of food safety.
Bhattacharyya
Sumit
S
Department of Medicine, University of Illinois, Chicago, Illinois 60612, USA.
Gill
Ravinder
R
Chen
Mei Ling
ML
Zhang
Fuming
F
Linhardt
Robert J
RJ
Dudeja
Pradeep K
PK
Tobacman
Joanne K
JK
D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D000818:Animals; D000074018:B-Cell CLL-Lymphoma 10 Protein; D002351:Carrageenan / Q000378:metabolism*; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism*; D006801:Humans; D007249:Inflammation; D016209:Interleukin-8 / Q000378:metabolism*; D007413:Intestinal Mucosa / Q000378:metabolism*; D008264:Macrophages / Q000378:metabolism; D051379:Mice; D016328:NF-kappa B / Q000378:metabolism*; D011485:Protein Binding; D051197:Toll-Like Receptor 4 / Q000378:metabolism / Q000502:physiology*
D048868:Adaptor Proteins, Signal Transducing; D000074018:B-Cell CLL-Lymphoma 10 Protein; C118591:BCL10 protein, human; D016209:Interleukin-8; D016328:NF-kappa B; D051197:Toll-Like Receptor 4; D002351:Carrageenan