Dll4 Suppresses Transcytosis for Arterial Blood-Retinal Barrier Homeostasis

Circ Res. 2020 Mar 13;126(6):767-783. doi: 10.1161/CIRCRESAHA.119.316476. Epub 2020 Feb 12.


Rationale: Central nervous system has low vascular permeability by organizing tight junction (TJ) and limiting endothelial transcytosis. While TJ has long been considered to be responsible for vascular barrier in central nervous system, suppressed transcytosis in endothelial cells 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 vascular barrier in central nervous system 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 endothelial cells, leading to nonhemorrhagic leakage predominantly in the superficial retinal layer. Endothelial Sox17 deletion represses Dll4 in retinal arteries, phenocopying Dll4 blocking-driven vascular leakage. Ang II (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 endothelial cells suggests that Dll4 blocking activates SREBP1 (sterol regulatory element-binding protein 1)-mediated lipogenic transcription and enriches gene sets favorable for caveolae formation. Profiling also predicts the activation of VEGF (vascular endothelial growth factor) signaling by Dll4 blockade. Inhibition of SREBP1 or VEGF-VEGFR2 (VEGF receptor 2) 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.

Keywords: caveolae; edema; hypertension; retinal artery; tight junctions; transcytosis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing / genetics
  • Adaptor Proteins, Signal Transducing / metabolism*
  • Animals
  • Arteries / metabolism
  • Blood-Retinal Barrier / metabolism*
  • Calcium-Binding Proteins / genetics
  • Calcium-Binding Proteins / metabolism*
  • Caveolae / metabolism
  • Endothelial Cells / metabolism
  • HMGB Proteins / metabolism
  • Homeostasis
  • Hypertensive Retinopathy / metabolism*
  • Mice
  • Mice, Inbred C57BL
  • Receptor, Notch1 / genetics
  • Receptor, Notch1 / metabolism
  • SOXF Transcription Factors / metabolism
  • Signal Transduction
  • Sterol Regulatory Element Binding Protein 1 / metabolism
  • Tight Junctions / metabolism
  • Transcytosis*
  • Vascular Endothelial Growth Factor A / metabolism
  • Vascular Endothelial Growth Factor Receptor-2 / metabolism


  • Adaptor Proteins, Signal Transducing
  • Calcium-Binding Proteins
  • DLL4 protein, mouse
  • HMGB Proteins
  • Notch1 protein, mouse
  • Receptor, Notch1
  • SOXF Transcription Factors
  • Sox17 protein, mouse
  • Srebf1 protein, mouse
  • Sterol Regulatory Element Binding Protein 1
  • Vascular Endothelial Growth Factor A
  • Kdr protein, mouse
  • Vascular Endothelial Growth Factor Receptor-2