Mouse and human Notch-1 regulate mucosal immune responses.

The Notch-1 signaling pathway is responsible for homeostatic tight junction expression in vitro, and promotes barrier function in vivo in the RAG1-adoptive transfer model of colitis. In this study, we sought to determine the role of colonic Notch-1 in the lymphoepithelial crosstalk in health and disease. We utilized in vivo and in vitro knockdown to target the expression of Notch-1. We identified that epithelial Notch-1 is required for appropriate activation of intestinal epithelial cells at steady state and upon inflammatory stimulus. Notch-1 expression modulates mucosal chemokine and cytokine secretion, and FoxP3 and effector T-cell responses. We showed that epithelial Notch-1 controls the immune function of the epithelium through crosstalk with the nuclear factor-κB (NF-κB)/mitogen-activated protein kinase (MAPK) pathways that, in turn, elicits T-cell responses. Overall, epithelial Notch-1 bridges innate and adaptive immunity in the gut. Our findings highlight an indispensable role for Notch-1-mediated signaling in the intricate epithelial-immune crosstalk, and validate that epithelial Notch-1 is necessary and sufficient to support protective epithelial proinflammatory responses.