Rationale: Central nervous system (CNS) has low vascular permeability by organizing tight junction (TJ) and limiting endothelial transcytosis. While TJ has long been considered to be responsible for barrier in CNS vessels, suppressed transcytosis in endothelial cells (ECs) is now emerging as a complementary mechanism. Whether transcytosis regulation is independent of TJ and its dysregulation dominantly causes diseases associated with edema remain elusive. Dll4 signaling is important for various vascular contexts but its role in the maintenance of CNS vascular barrier remains unknown. Objective: To find a TJ-independent regulatory mechanism selective for transcytosis and identify its dysregulation as a cause of pathological leakage. Methods and Results: We studied transcytosis in the adult mouse retina with low vascular permeability and employed a hypertension-induced retinal edema model for its pathological implication. Both antibody-based and genetic inactivation of Dll4 or Notch1 induce hyperpermeability by increasing transcytosis without junctional destabilization in arterial ECs, leading to non-hemorrhagic leakage predominantly in the superficial retinal layer. Endothelial Sox17 deletion represses Dll4 in retinal arteries, phenocopying Dll4 blocking-driven vascular leakage. Angiotensin II-induced hypertension represses arterial Sox17 and Dll4, followed by transcytosis-driven retinal edema, which is rescued by a gain of Notch activity. Transcriptomic profiling of retinal ECs suggests that Dll4 blocking activates SREBP1-mediated lipogenic transcription and enriches gene sets favorable for caveolae formation. Profiling also predicts the activation of VEGF signaling by Dll4 blockade. Inhibition of SREBP1 or VEGF-VEGFR2 signaling attenuates both Dll4 blockade-driven and hypertension-induced retinal leakage. Conclusions: In the retina, Sox17-Dll4-SREBP1 signaling axis controls transcytosis independently of TJ in superficial arteries among heterogeneous regulations for the whole vessels. Uncontrolled transcytosis via dysregulated Dll4 underlies pathological leakage in hypertensive retina and could be a therapeutic target for treating hypertension-associated retinal edema.

中文翻译：

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Dll4抑制动脉血液-视网膜屏障稳态的转胞作用。

理由：中枢神经系统（CNS）通过组织紧密连接（TJ）和限制内皮细胞的胞吞作用而具有较低的血管通透性。尽管长期以来一直认为TJ是中枢神经系统血管屏障的原因，但内皮细胞（ECs）中抑制转吞作用的作用正逐渐成为一种补充机制。转胞吞调节是否独立于TJ以及其失调主要导致与水肿相关的疾病仍然难以捉摸。Dll4信号对于各种血管情况都很重要，但其在中枢神经系统血管屏障维持中的作用仍然未知。目的：寻找一种选择性的TJ独立调节机制来进行转胞吞作用，并确定其失调是病理性渗漏的原因。方法和结果：我们研究了具有低血管通透性的成年小鼠视网膜的转胞吞作用，并采用了高血压诱导的视网膜水肿模型进行病理学研究。Dll4或Notch1的基于抗体的和基因的失活都通过增加细胞吞噬作用而不引起动脉EC的连接不稳定来诱导通透性过高，从而导致非出血性渗漏主要发生在浅视网膜层。内皮细胞Sox17缺失抑制视网膜动脉中的Dll4，表型复制Dll4阻断驱动的血管渗漏。血管紧张素II诱导的高血压会抑制动脉Sox17和Dll4，然后再由胞吞作用驱动的视网膜水肿抑制，而Notch活性可以缓解视网膜水肿。视网膜ECs的转录组分析表明，Dll4阻断激活了SREBP1介导的脂肪生成，并丰富了有利于海绵体形成的基因集。分析还预测了Dll4阻断对VEGF信号传导的激活。SREBP1或VEGF-VEGFR2信号的抑制减弱了Dll4阻滞驱动和高血压引起的视网膜渗漏。结论：在视网膜中，Sox17-Dll4-SREBP1信号轴独立于TJ在整个血管的异质调节之间控制着浅表动脉的转细胞作用。经由失调的Dll4的不受控制的转胞吞作用是高血压视网膜中病理性渗漏的基础，并且可能是治疗与高血压相关的视网膜水肿的治疗靶标。SREBP1或VEGF-VEGFR2信号的抑制减弱了Dll4阻滞驱动和高血压引起的视网膜渗漏。结论：在视网膜中，Sox17-Dll4-SREBP1信号轴独立于TJ在整个血管的异质调节之间控制着浅表动脉的转细胞作用。经由失调的Dll4的不受控制的转胞吞作用是高血压视网膜中病理性渗漏的基础，并且可能是治疗与高血压相关的视网膜水肿的治疗靶标。SREBP1或VEGF-VEGFR2信号的抑制减弱了Dll4阻滞驱动和高血压引起的视网膜渗漏。结论：在视网膜中，Sox17-Dll4-SREBP1信号轴独立于TJ在整个血管的异质调节之间控制着浅表动脉的转细胞作用。经由失调的Dll4的不受控制的转胞吞作用是高血压视网膜中病理性渗漏的基础，并且可能是治疗与高血压相关的视网膜水肿的治疗靶标。