Opposing Regulation of the Tight Junction Protein Claudin-2 by Interferon-γ and Interleukin-4

Background: The claudins are tight junction (TJ) proteins. Claudin-2 has been found to negatively affect the TJ, causing a decrease in transepithelial resistance. Patients with inflammatory bowel disease have altered intestinal permeability, suggesting a TJ disruption. Interferon-gamma (IFNγ) and interleukin-4 (IL-4) negatively regulate each other and may have opposing roles in inflammatory bowel disease. Hypothesis: IFNγ and IL-4 will have opposing effects on the expression of claudin-2. Methods: Confluent T84 monolayers were apically incubated with IFNγ or IL-4. The monolayers were immunofluorescently stained or lysed for Western blot with anti-claudin-2 or -4. Additional monolayers were grown on transwell plates, treated with IFNγ or IL-4, measured for changes in transepithelial resistance, and assayed for changes in permeability using FITC-dextran-4000. Statistics were calculated by analysis of variance. Results: Addition of IFNγ to T84 monolayers resulted in decreased claudin-2 and addition of IL-4 resulted in increased claudin-2 by Western blot. By immunofluorescence, there was a loss of claudin-2 from the membrane in cells treated with IFNγ. Transepithelial resistance across T84 monolayers increased with IFNγ and decreased with IL-4. T84 monolayer permeability increased with IL-4 but not with IFNγ. Conclusions: Incubation of T84 cells with IL-4 leads to increased claudin-2 with a corresponding decrease in transepithelial resistance and increase in permeability. Incubation of T84 cells with IFNγ leads to decreased claudin-2 and increased transepithelial resistance. These cytokines have opposite effects on the expression of claudin-2 and the physiology of the TJ.