Intestinal epithelial cells as producers but not targets of chronic TNF suffice to cause murine Crohn-like pathology

摘要

TNF plays a crucial role in the pathogenesis of Crohn disease. Dys-regulated TNF production in mice that bear the genetic deletion of the TNF AU-rich regulatory elements (ARE) (Tnf~(△ARE/+) mice) results in TNF receptor I (TNFRI)-dependent spontaneous Crohn-like pathology. Current concepts consider intestinal epithelial cell (IEC) responses to TNF to be critical for intestinal pathology, but the potential contribution of lEC-derived TNF in disease pathogenesis has not been addressed. In this study we examined whether IEC are sufficient as cellular targets or sources of TNF in the development of intestinal pathology. Using lEC-specific reactivation of a hypomorphic Tnf△AREneoallele in mice, we show that selective chronic overproduction of TNF by IEC suffices to cause full development of Crohn-like pathology. Epithelial TNF overexpression leads to early activation of the underlying intestinal myofibro-blast, a cell type previously identified as a sufficient target of TNF for disease development in the Tnf△ARE model. By contrast, restricted TNFRI expression on IEC although sufficient to confer IEC apoptosis after acute exogenous TNF administration, fails to induce pathology following chronic specific targeting of IEC by endogenous TNF in Tnf△ARE/+ mice. Our results argue against IEC being early and sufficient responders to chronic TNF-mediated pathogenic signals and suggest that proinflammatory aberrations leading to chronic TNF production by IEC may initiate pathology in Crohn disease.