Lipopolysaccharide transport system across colonic epithelial cells in normal and infective rat

To clarify whether lipopolysaccharide (LPS) is transported in rat intestinal epithelial cells, the transport of FITC-LPS across colonic epithelial cells in normal and LPS-exposured rats using a diffusion chamber was examined. The expression of CD14 and Toll-like receptor 4 (TLR4) was also examined. Rats were given 10 mg/kg LPS i.p. injection at 4 hr prior to the isolation of colonic epithelial tissues. The permeation rate across colonic mucosa by FITC-LPS was several times greater in the mucosal to serosal (M to S) direction than in the opposite direction in both normal and LPS-exposured rats. Increased M to S permeation by FITC-LPS was evident at 37 degrees C, but not at 4 degrees C. The permeability of FITC-LPS in both the M to S and S to M directions was inhibited by unlabeled LPS, anti-CD14 antibody or anti-TRL4 antibody in normal rat. In LPS-exposured rat, the inhibition in the M to S direction was observed by anti-TLR4 antibody, but not by unlabeled LPS and anti- CD14 antibody. In contrast, the permeability in the S to M direction was decreased only by unlabeled LPS in LPS-exposured rat. In normal rat, the expression of CD14 and TLR4 was found in the mucosal and serosal sides. In LPS-exposured rat, the expression of CD14 was not observed in the mucosal side. The electrophysiological parameters by LPS exposure remain unchanged. These findings suggest the possibility that colonic epithelial cells contain specific transport systems for LPS, one of which shows some degree of substrate specificity with the interaction of CD14 and/or that of TLR4.