Endothelial sensing of AHR ligands regulates intestinal homeostasis

Abstract The blood and lymphatic vasculature is lined by functionally specialised endothelial cells (ECs). Vascular beds act as an essential physical barrier, control nutrient transport, facilitate tissue immunosurveillance, and coordinate angiogenesis and lymphangiogenesis to ensure appropriate tissue perfusion and drainage 1,2 . Conversely, vascular maladaptation can lead to pathological angiogenesis and the perpetuation of inflammation in chronic inflammatory diseases 3,4 . In the intestine, dietary and microbial cues are particularly important in regulation of organ homeostasis. However, whether enteric ECs actively sense and integrate such signals is currently unknown. Here, we show that the aryl hydrocarbon receptor (AHR), a ligand-activated transcription factor, acts as critical node for EC-sensing of dietary metabolites in adult mice and human primary ECs. We first established a comprehensive single-cell endothelial atlas of the mouse small intestine, uncovering the cellular complexity and functional heterogeneity of blood and lymphatic ECs. Analyses of AHR mediated responses at single-cell resolution identified tissue-protective transcriptional signatures and regulatory networks promoting cellular quiescence and vascular normalcy at steady state. Endothelial AHR-deficiency in adult mice resulted in dysregulated inflammatory responses, and initiation of proliferative and angiogenic pathways. Furthermore, endothelial sensing of dietary AHR ligands was required for optimal protection against enteric infection. In human ECs, AHR signalling promoted quiescence and restrained activation by inflammatory mediators. Together, our data provide a comprehensive dissection of the impact of environmental sensing across the spectrum of enteric endothelia, demonstrating that endothelial AHR signalling integrates dietary cues to maintain tissue homeostasis by promoting EC quiescence and normalcy.