Interferon-γ modulates intestinal epithelial cell function in-vitro through a TGFβ-dependent mechanism

Introduction: Interferon gamma (IFN gamma) has been originally identified by its anti-viral activity and has been demonstrated to act as potent modulator of the immune system with a range of target cells limited largely to immune cell populations. Although IFN gamma has been shown to directly affect the barrier function of intestinal epithelial cells, only limited information is available about other functional effects of IFN gamma on intestinal epithelial cells. Methods: The effects on intestinal epithelial cell migration were studied using a previously described in-vitro model of epithelial restitution in confluent IEC-6 cell monolayers. Intestinal epithelial cell proliferation rates were assessed in various human and rat intestinal and colon epithelial cell lines using colorimetric MTT assays. Apoptosis of IEC-6 cells exposed to IFN gamma was assessed by flow cytometry. In addition, transforming growth factor beta mRNA expression after IFN gamma treatment of IEC-6 cells was assessed by Northern blot analysis. Results: IFN gamma significantly stimulated intestinal epithelial cell migration in an in-vitro wounding model. Furthermore, IFN gamma caused a significant dose-dependent inhibition of epithelial cell proliferation in non-transformed small intestinal IEC-6 cells and human colon cancer-derived HT-29 cells and no significant rates of apoptosis were detected in the exposed epithelial cells. The effect of IFN gamma on epithelial cell migration and proliferation could be completely blocked by neutralizing antibodies against TGF beta indicating that these effects are mediated through a TGF beta dependent pathway. In addition, increased expression of TGF beta 1 mRNA by IEC-6 cells after treatment with IFN gamma supports the hypothesis that IFN gamma modulates intestinal epithelial cell function through a TGF beta-dependent pathway. Conclusion: These studies suggest that IFN gamma produced by constituents of the mucosal immune system modulates epithelial cell functions with relevance for intestinal wound healing and may play a role in preserving the integrity of the intestinal epithelium following various forms of injuries. (C) 2011 Elsevier B.V. All rights reserved.