Abstract 14824: Reduced Endothelial ADAR1-Dependent RNA Editing Induces NOCT-Driven Immunoactivation and Promotes Pulmonary Hypertension

• Published in: Circulation (New York, N.Y.) N.Y.), 2023-11, Vol.148 (Suppl_1)
• Main Authors: Woodcock, Chen-Shan J, Maroli, Giovanni, Kim, Hyunbum, Tang, Ying, Tai, Yi Yin, Okawa, Satoshi, Cho, Shu-Ting, Lafyatis, Robert, Chauvet, Caroline, Kudryashova, Tatiana, Goncharova, Elena A, Bertero, Thomas, Yuan, Ke, Pullamsetti, Soni, Chan, Stephen Y
• Format: Article
• Language: English
• ISSN: 0009-7322; 1524-4539
• DOI: 10.1161/circ.148.suppl_1.14824

Abstract only Introduction: Early apoptosis of pulmonary artery endothelial cells (PAECs) is a key driver of vascular remodeling and pulmonary hypertension (PH), but its regulation is poorly defined. Adenosine deaminase acting on RNA 1 (ADAR1) is an RNA editing enzyme that converts adenosine to inosine (A-to-I) in RNA transcripts. We found that ADAR1 expression was reduced in PH endothelium. While reduced RNA editing stimulates aberrant cytosolic innate immunity and can drive apoptosis, the exact RNA editing targets and downstream mechanisms regulating pulmonary endothelial survival are unknown. Hypothesis: Deficiency in ADAR1-mediated RNA editing promotes pulmonary endothelial pathophenotypes and drives PH. Methods & Results: ADAR1 expression was downregulated in the pulmonary vascular endothelium and in lung tissues of human and mouse PH. Global A-to-I editing was decreased in the whole lungs and PBMCs from PAH patients. In vitro , hypoxia, a known PH trigger, downregulated ADAR1 in PAECs via upregulation of the ADAR1-targeting microRNA, miR-17. By RNA sequencing of PAECs after ADAR1 knockdown, we identified the circadian gene Nocturnin ( NOCT ) as a direct ADAR1 target that carries two active A-to-I RNA editing sites in the 3’UTR. By single cell RNA sequencing of human PAH lungs, NOCT editing levels were reduced, while NOCT transcript levels increased. Correspondingly, in vitro , ADAR1 silencing increased NOCT mRNA levels, thus activating an innate immune response and PAEC apoptosis. Forced NOCT expression phenocopied the effect of ADAR1 deficiency, inducing RNA sensing innate immunity signaling pathway and increasing apoptosis. In vivo , in mice chronically exposed to hypoxia, administration of the ADAR1 inhibitor 8-Azaadenosine (Aza) resulted in worsened indices of PH. Notably, genetic deletion of NOCT mitigated PH induced by Aza in hypoxic IL6 transgenic mice, emphasizing the crucial role of NOCT in ADAR1-mediated pathogenesis. Conclusions: Hypoxia-induced ADAR1 deficiency promotes NOCT mRNA dysregulation to induce PAEC innate immunity, PAEC apoptosis, and PH. This study provides impetus to target the ADAR1-NOCT axis for more effective diagnostics and therapeutics for PH.