Compartmentalized Response of IL-6/STAT3 Signaling in the Colonic Mucosa Mediates Colitis Development

A single layer of polarized epithelial cells lining the colonic mucosa create a semipermeable barrier indispensable for gut homeostasis. The role of intestinal epithelial cell (IEC) polarization in the maintenance of the epithelial homeostasis and in the development of inflammatory bowel diseases is not fully understood. In this review, now we report that IEC polarization plays an essential role in the regulation of IL-6/STAT3 signaling in the colonic mucosa. Our results demonstrate that autocrine STAT3 activation in IECs is mediated by the apical secretion of IL-6 in response to the basolateral stimulation with IFN-γ. This process relies on the presence of functional, IFN-γ-producing CD4⁺ T cells. In the absence of basolateral IFN-γ, the compartmentalization of the IL-6/STAT3 signaling is disrupted, and STAT3 is activated mainly in macrophages. Thus, in this study, we show that during inflammation, IFN-γ regulates IL-6/STAT3 signaling in IEC in the colonic mucosa.