INTERLEUKIN-6 AND TUMOR-NECROSIS-FACTOR PRODUCTION IN AN ENTEROCYTE CELL MODEL (CACO-2) DURING EXPOSURE TO ESCHERICHIA-COLI

Data linking interactions between bacteria and the intestine with elev ated serum cytokine levels has led to the concept of the gut as a cyto kine-producing organ. An in vitro cell culture model was used to inves tigate the potential role of intestinal mucosa within this paradigm. P olarized monolayers of human enterocytes (Caco-2) were grown in a two compartment system where the apical and basal aspects of the membrane could be studied. Supernatant was collected at 0, 1, 3, 6, and 24 h af ter the monolayer was exposed (apically or basally) to 10(2), 10(5), o r 10(8) colony-forming units of Escherichia coli C25/mL and saved for interleukin (IL)-6 and tumor necrosis factor (TNF) bioassay analysis. Caco-2 cells (not bacterially challenged) secreted significant amounts of constitutive IL-6, but not TNF, into the apical and basal chambers . Both cytokines levels were increased in a dose-dependent fashion (p <.05) after the E. coli challenge. This stimulated cytokine response w as polar, in that the highest cytokine levels were at the side of the bacterial challenge and were most notable at the highest dose (10(8) c olony-forming units/mL) of E. coli C25 tested. Caco-2 cells produce IL -6 and TNF in a dose-dependent fashion in response to E. coli C25 and the magnitude of this response is maximal on the side of the bacterial challenge. This data supports the hypothesis that bacterially challen ged human enterocytes may be important producers of cytokines.