Abstract 19574: Adenosine Deaminase Acting on RNA-1 is Indispensable for Vascular Development and Homeostasis in vivo
Introduction: Adenosine deaminase acting on RNA-1 (ADAR1) binds to double-stranded RNAs and mediates adenosine to inosine RNA editing, which is a widespread post-transcriptional mechanism in mammals that affects several coding and regulatory RNAs, by altering their sequence and structure. However, the role of endothelial cell ADAR1 in vascular homeostasis has not been reported so far.
Methods and Results: To investigate the role of ADAR1 in vascular development, ADAR1flox/flox mice were inbred with Tie2-Cre mice. The EC restricted ADAR1 knockout mice resulted in embryonic death at E13.5, suggesting an essential role for endothelial ADAR1 in embryonic development. To evaluate the role of ADAR1 in postnatal retinal vascular development, ADAR1flox/flox mice were inbred with mice carrying a tamoxifen-inducible VE-Cadherin-Cre transgene (Cdh5-CreERT2) creating an inducible endothelial cell-restricted ADAR1 knockout (iEC-ADAR1 KO) mouse model. Postnatal ADAR1 ablation resulted in 24±4% reduced vascular outgrowth, 18±7% reduced vessel branching in the central vascular plexus and 39±11%-decreased filopodial protrusions from endothelial cells at the angiogenic front of the vascular plexus compared with littermate control mice at P5 (all P<0.05). Furthermore, endothelial cell ablation of ADAR1 in 8-week old mice resulted in formation of pleural effusion and ascites, indicating a disturbance of endothelial cell barrier function, with subsequent death within 6-8 days after ADAR1 ablation (log rank P<0.001 of the Kaplan-Meier survival curve for n=12 mice per group). Histological analysis of the lung tissues revealed the presence of apoptotic endothelial cells, indicating that ADAR1 plays a critical role in endothelial cell homeostasis in vivo. Mechanistically, ADAR1 knockdown in ECs induced a dsRNA-induced innate immune response as observed by activation of the cytosolic dsRNA receptor MDA5, upregulation of interferon-beta expression, increased apoptotic signalling and defective endothelial cell-cell junctional integrity as assessed by VE-cadherin staining.
Conclusions: ADAR1 is critically involved in the prevention of innate immune sensing and endothelial cell barrier dysfunction by self-dsRNA and thus vascular homeostasis in vivo.
Author Disclosures: F. Lunella: None. A. Gatsiou: None. P. Grote: None. C. Amrhein: None. A. Doddaballapur: None. E. Chavakis: None. T. Braun: None. A. Zeiher: None. S. Dimmeler: None. K. Stellos: None.
- © 2016 by American Heart Association, Inc.