Interleukin-4 and interleukin-13 differentially regulate epithelial chloride secretion

Intestinal epithelia are in intimate contact with subepithelial and intraepithelial lymphocytes. When stimulated, mucosal lymphocytes generate cytokines that act locally and influence functional aspects of many cell types. We have previously defined functional epithelial receptors for interferon-gamma, interleukin (IL)-4, and a recently described IL-4-like cytokine IL-13. In this study, we examine the ion transport properties of T84 cells, a crypt-like epithelial cell line, following exposure to IL-4 and IL-13. Basolateral exposure of epithelial monolayers to both IL-4 and IL-13 attenuated epithelial barrier function and increased paracellular flux of a dextran marker by greater than 65% in a dose- and time-dependent fashion. Stimulated Cl- secretion, as measured by epithelial short circuit current, however, was diminished only by IL-4 and not IL-13, demonstrating cytokine specificity in this epithelial function. Decreased Cl- secretion following IL-4 exposure was associated with diminished Cl- channel activity and IL-4 pretreatment of epithelia decreased expression of the cystic fibrosis transmembrane regulator. Finally, stimulated fluid transport across cultured epithelia was diminished following exposure to IL-4, but not IL-13. These results indicate that while post-receptor signaling events induced by IL-13 and IL-4 may be similar, end point function is cytokine-specific.