Lung epithelial barrier function and wound healing are decreased by IL-4 and IL-13 and enhanced by IFN-γ

Abstract

To understand the effects of cytokines on epithelial cells in asthma, we have investigated the effects of interleukin (IL)-4, IL-13, and interferon (IFN)-γ on barrier function and wound healing in Calu-3 human lung epithelial cells. IL-4 and IL-13 treatment of Calu-3 cells grown on Transwell filters resulted in a 70–75% decrease in barrier function as assessed by electrophysiological and [14C]mannitol flux measurements. In contrast, IFN-γ enhanced barrier function threefold using these same parameters. Cells treated concurrently with IFN-γ and IL-4 or IL-13 showed an initial decline in barrier function that was reversed within 2 days, resulting in barrier levels comparable to control cells. Analysis of the tight junction-associated proteins ZO-1 and occludin showed that IL-4 and IL-13 significantly reduced ZO-1 expression and modestly decreased occludin expression compared with controls. IFN-γ, quite unexpectedly given its enhancing effect on barrier function, reduced expression of ZO-1 and occludin to almost undetectable levels compared with controls. In wound-healing assays of cells grown on collagen I, IL-4 and IL-13 decreased migration, whereas IFN-γ treatment enhanced migration, compared with control cells. Addition of IFN-γ, in combination with IL-4 or IL-13, restored migration of cells to control levels. Migration differences observed between the various cytokine treatments was correlated with expression of the collagen I-binding α2β1-integrin at the leading edge of cells at the wound front; α2β1-integrin expression was decreased in IFN-γ-treated cells compared with controls, whereas it was highest in IL-4- and IL-13-treated cells. These results demonstrate that IL-4 and IL-13 diminish the capacity of Calu-3 cells to maintain barrier function and repair wounds, whereas IFN-γ promotes epithelial restitution by enhancing barrier function and wound healing.