Polarized secretion of IL-6 by IEC-6 intestinal epithelial cells: differential effects of IL-1 beta and TNF-alpha

Intestinal epithelial cells (IEC) can exist as polarized cells and are capable of secreting interleukin-6 (IL-6), yet it has not been determined if this IL-6 is secreted in a polarized fashion. Using the non-transformed rat IEC-6 intestinal epithelial cell line grown on microporous membrane inserts, we have determined that these cells were capable of secreting IL-6 preferentially to the basal surface when stimulated basally with IL-1 beta. In contrast, stimulation of the cells with TNF-alpha resulted in an equal level of IL-6 secretion to the apical and basal surfaces, regardless of whether the cells were stimulated by the apical or basal route. Experiments designed to test the permeability of the IEC-6 cell layer to apically added sodium fluorescein confirmed that neither IL-1 beta nor TNF-alpha altered the integrity of the cell layer after three days. These results suggest that IEC may have the capacity to secret IL-6 in different patterns depending upon the stimulation received. This would allow communication between the IEC and lamina propria cells via basal secretion and rapid communication between IEC via apical secretion.