Role of mucin, mannose, and beta-1 integrin receptors in Escherichia coli translocation across Caco-2 cell monolayers.

Our previous work suggests that Caco-2 cells play an active role in bacterial translocation (BT). Since bacterial enterocyte interactions may be receptor-mediated, the current study was performed to investigate the role of beta 1 integrin and mannose receptors as well as the general protective effect of the mucous layer in this process. Caco-2 cells grown to confluence on semipermeable membranes contained in the upper compartment of a two compartment system were utilized. BT was assessed by quantitating the number of Escherichia coli crossing the monolayers after challenge with 10(8) E. coli C25. Pretreatment of the Caco-2 cells with the beta 1 integrin receptor competitive inhibitors fibronectin or RGD did not inhibit BT; while pretreatment of Caco-2 cells with the LFA-1 (lectin) receptor competitive inhibitor mannose (12 mg/ml) or purified mucin (8 mg/ml) decreased BT compared to control membranes (p < .001). Transepithelial resistance was similar among all the groups indicating maintenance of tight junction integrity. These studies suggest that E. coli BT in the Caco-2 system can be reduced by mannose and that intestinal mucin contributes to the barrier function of the monolayer.