Endothelial sensing of AHR ligands regulates intestinal barrier immunity [BEC_SI]. Endothelial sensing of AHR ligands regulates intestinal barrier immunity [BEC_SI]

The blood and lymphatic vasculature is lined by functionally specialised endothelial cells (ECs). In the intestine, ECs act as an essential physical barrier, controlling nutrient transport, facilitating tissue immunosurveillance, and coordinating angiogenesis and lymphangiogenesis to ensure appropriate tissue perfusion and drainage. Conversely, endothelial maladaptation can lead to pathological angiogenesis and the perpetuation of inflammation in chronic inflammatory diseases. However, whether enteric ECs actively engage in the regulation of intestinal homeostasis and pathology through integration of environmental cues 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 and microbial metabolites. 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, identifying transcriptional networks and putative biological roles across endothelial subtypes. Analyses of AHR mediated responses at single-cell resolution identified tissue-protective transcriptional signatures and regulatory networks promoting quiescence and vasculoprotection. Endothelial AHR-deficiency in mice resulted in cellular activation, proliferation, and initiation of angiogenic pathways disrupting tissue homeostasis. In human ECs, AHR signalling promoted quiescence through cell cycle arrest and tempered endothelial inflammatory responses. Together, our data provide a comprehensive dissection of the impact of environmental sensing across the spectrum of enteric endothelia, demonstrating that endothelial AHR signalling serves to promote homeostasis and prevent aberrant inflammatory responses at the intestinal barrier. Overall design: Examination of AHR-deficient (VeciCre x AHR flfl x NuTRAP) vs control (VeciCre x NuTRAP) mice small intestinal blood endothelial cell transcriptomes by bulk RNA sequencing.

血液及淋巴脉管系统由具备功能特化属性的内皮细胞（endothelial cells, ECs）所衬贴。在肠道中，内皮细胞作为不可或缺的物理屏障，调控营养物质转运、辅助组织免疫监视，并协调血管生成与淋巴管生成，以保障组织的正常灌注与淋巴引流。反之，内皮细胞的适应不良可引发病理性血管生成，并加剧慢性炎症性疾病中的炎症持续状态。然而，肠道内皮细胞是否通过整合环境信号主动参与肠道稳态与病理进程的调控，目前仍未明确。本研究显示，芳香烃受体（aryl hydrocarbon receptor, AHR）作为配体激活型转录因子，是内皮细胞感知膳食与微生物代谢物的关键调控节点。我们首先构建了小鼠小肠的全面单细胞内皮细胞图谱，揭示了血液与淋巴内皮细胞的细胞复杂性与功能异质性，并明确了不同内皮细胞亚型的转录调控网络及推定生物学功能。通过单细胞分辨率下的AHR介导应答分析，我们鉴定出了促进细胞静息与血管保护的组织保护性转录特征及调控网络。小鼠体内内皮细胞AHR缺陷会导致细胞活化、增殖，并启动破坏组织稳态的血管生成通路。在人类内皮细胞中，AHR信号通路通过细胞周期阻滞促进细胞静息，并抑制内皮细胞的炎症应答。综上，本研究的数据全面解析了环境感知对各类肠道内皮细胞的影响，证实内皮细胞AHR信号通路可促进肠道屏障稳态，并抑制异常炎症应答。实验设计：通过批量RNA测序，对比分析AHR缺陷型（VeciCre × AHR flfl × NuTRAP）与对照型（VeciCre × NuTRAP）小鼠的小肠血液内皮细胞转录组。