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

INTRODUCTION

Interferon γ (IFNγ) 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 IFNγ has been shown to directly affect the barrier function of intestinal epithelial cells, only limited information is available about other functional effects of IFNγ 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 IFNγ was assessed by flow cytometry. In addition, transforming growth factor β mRNA expression after IFNγ treatment of IEC-6 cells was assessed by Northern blot analysis.

RESULTS

IFNγ significantly stimulated intestinal epithelial cell migration in an in-vitro wounding model. Furthermore, IFNγ 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 IFNγ on epithelial cell migration and proliferation could be completely blocked by neutralizing antibodies against TGFβ indicating that these effects are mediated through a TGFβ dependent pathway. In addition, increased expression of TGFβ1 mRNA by IEC-6 cells after treatment with IFNγ supports the hypothesis that IFNγ modulates intestinal epithelial cell function through a TGFβ-dependent pathway.

CONCLUSION

These studies suggest that IFNγ 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.