TY - JOUR
T1 - Toll-like receptor 2-mediated peptidoglycan uptake by immature intestinal epithelial cells from apical side and exosome-associated transcellular transcytosis
AU - Bu, Heng Fu
AU - Wang, Xiao
AU - Tang, Yi
AU - Koti, Viola
AU - Tan, Xiao Di
PY - 2010/3
Y1 - 2010/3
N2 - Peptidoglycan (PGN) is a potent immune adjuvant derived from bacterial cell walls. Previous investigations suggest that intestinal epithelium may absorbPGN from the lumen. Nonetheless, how PGN is taken up and crosses intestinal epithelium remains largely unclear. Here, we first characterized PGN transport in vitro using IEC-18 and HT29-CL19A cells, which represent less mature epithelial cells in intestinal crypts. With fluorescent microscopy, we visualized internalization of dual-labeledPGNby enterocytes. EngulfedPGNwas found to form a complex with PGN recognition protein-3, which may facilitate delivering PGN in vivo. Utilizing electronic microscopy, we revealed that uptake of apicalPGNacross intestinal epithelial monolayers was involved in phagocytosis, multivesicular body formation, and exosome secretion. We also studied transport of PGN using the transwell system. Our data indicated that apically loaded PGN was exocytosed to the basolateral compartment with exosomes by HT29-CL19A cells. The PGN-contained basolateral exosome extracts induced macrophage activation. Through gavaging mice with labeled PGN, we found that luminal PGN was taken up by columnar epithelial cells in crypts of the small intestine. Furthermore, we showed that pre-confluent immature but not post-confluent mature C2BBe1 cells engulfed PGN via a toll-like receptor 2-dependent manner. Together, our findings suggest that (1) crypt-based immature intestinal epithelial cells play an important role in transport of luminal PGN over the intestinal epithelium; and (2) luminalPGNis transcytosed across intestinal epithelia via a toll-like receptor 2-mediated phagocytosis- multivesicular body-exosome pathway. The absorbed PGN and its derivatives may facilitate maintenance of intestinal immune homeostasis.
AB - Peptidoglycan (PGN) is a potent immune adjuvant derived from bacterial cell walls. Previous investigations suggest that intestinal epithelium may absorbPGN from the lumen. Nonetheless, how PGN is taken up and crosses intestinal epithelium remains largely unclear. Here, we first characterized PGN transport in vitro using IEC-18 and HT29-CL19A cells, which represent less mature epithelial cells in intestinal crypts. With fluorescent microscopy, we visualized internalization of dual-labeledPGNby enterocytes. EngulfedPGNwas found to form a complex with PGN recognition protein-3, which may facilitate delivering PGN in vivo. Utilizing electronic microscopy, we revealed that uptake of apicalPGNacross intestinal epithelial monolayers was involved in phagocytosis, multivesicular body formation, and exosome secretion. We also studied transport of PGN using the transwell system. Our data indicated that apically loaded PGN was exocytosed to the basolateral compartment with exosomes by HT29-CL19A cells. The PGN-contained basolateral exosome extracts induced macrophage activation. Through gavaging mice with labeled PGN, we found that luminal PGN was taken up by columnar epithelial cells in crypts of the small intestine. Furthermore, we showed that pre-confluent immature but not post-confluent mature C2BBe1 cells engulfed PGN via a toll-like receptor 2-dependent manner. Together, our findings suggest that (1) crypt-based immature intestinal epithelial cells play an important role in transport of luminal PGN over the intestinal epithelium; and (2) luminalPGNis transcytosed across intestinal epithelia via a toll-like receptor 2-mediated phagocytosis- multivesicular body-exosome pathway. The absorbed PGN and its derivatives may facilitate maintenance of intestinal immune homeostasis.
UR - http://www.scopus.com/inward/record.url?scp=73649083677&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=73649083677&partnerID=8YFLogxK
U2 - 10.1002/jcp.21985
DO - 10.1002/jcp.21985
M3 - Article
C2 - 20020500
AN - SCOPUS:73649083677
VL - 222
SP - 658
EP - 668
JO - Journal of Cellular Physiology
JF - Journal of Cellular Physiology
SN - 0021-9541
IS - 3
ER -