Intestinal epithelial barrier dysfunction and dendritic cell redistribution during early stages of inflammation in the rat: role for TLR-2 and -4 blockage.
BACKGROUND
Dendritic cell (DC) redistribution during early stages of enteritis may be related to ileal barrier dysfunction. We used a rat model of ileitis to examine this hypothesis.


METHODS
Sprague-Dawley rats were injected with indomethacin or saline and euthanized 2, 6, 12, or 24 hours later. Ileal segments and mesenteric lymph nodes were obtained for morphological, bacterial, or functional studies. To determine the role of Toll-like receptor (TLR)-2 and -4 blockages, rats were pretreated with normal IgG, anti-TLR-2, or anti-TLR-4 antibodies prior to indomethacin or saline, and ileal segments were collected 24 hours later.


RESULTS
In control rats, CD103+DC were mainly located in the lamina propria (LP) and some expressed TLR-2. TLR-4+ cells with different morphology and distribution from CD103+DC were also detected. In indomethacin-treated rats at 6-24 hours, inflammation was evident as was redistribution of CD103+DC from LP to Peyer's patches. We also observed TLR-2+ monocyte depletion and changes in TLR-4 distribution. At 2-6 hours we detected opened tight junctions as well as abnormal trans- and para-epithelial enteric bacterial infiltration, while macromolecular permeability was not significantly enhanced until 24 hours. In the absence of indomethacin, anti-TLR-2 blockage induced a significant increase of LP CD103+DC, while in the presence of indomethacin, anti-TLR-2 or -4 blockages significantly inhibited (P < 0.05) the reduction of LP CD103+DC.


CONCLUSIONS
During the early stages of indomethacin-induced ileitis, epithelial barrier damage and abnormal bacterial infiltration into the mucosa occurred in conjunction with initial redistribution of CD103+DC. Furthermore, we showed that TLR-2 and -4 blockade regulates CD103+DC distribution during early phases in this experimental model.
Silva
Manuel A
MA
Intestinal Disease Research Programme, Department of Pathology and Molecular Medicine, McMaster University, Ontario, Canada. msilvamu@hotmail.com
Jury
Jennifer
J
Porras
Mónica
M
Vergara
Patri
P
Perdue
Mary H
MH
D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000633:toxicity; D015703:Antigens, CD / Q000378:metabolism; D015153:Blotting, Western; D003713:Dendritic Cells / Q000378:metabolism* / Q000648:ultrastructure; D004195:Disease Models, Animal; D018450:Disease Progression; D020895:Enterocytes / Q000648:ultrastructure; D004847:Epithelial Cells / Q000378:metabolism* / Q000648:ultrastructure; D006735:Horseradish Peroxidase / Q000493:pharmacokinetics; D007079:Ileitis / Q000139:chemically induced / Q000378:metabolism* / Q000473:pathology; D007082:Ileum / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D007150:Immunohistochemistry; D007213:Indomethacin / Q000633:toxicity; D039001:Integrin alpha Chains / Q000378:metabolism; D007413:Intestinal Mucosa / Q000378:metabolism* / Q000473:pathology; D008297:Male; D008854:Microscopy, Electron; D010539:Permeability / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D051195:Toll-Like Receptor 2 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D051197:Toll-Like Receptor 4 / Q000037:antagonists & inhibitors* / Q000378:metabolism
D000894:Anti-Inflammatory Agents, Non-Steroidal; D015703:Antigens, CD; D039001:Integrin alpha Chains; C495343:Tlr2 protein, rat; C495347:Tlr4 protein, rat; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; C091367:alpha E integrins; D006735:Horseradish Peroxidase; D007213:Indomethacin