Abstract 10848: Adar1 Mediated Rna Editing Contributes to Vascular Remodeling

Abstract

Intro: Adenosine deaminases acting on RNA 1 (ADAR1) catalyzes the conversion of adenosine (A) to inosine (I) on RNA transcripts. Due to the host immune response to non-edited double-stranded RNAs, ADAR1 deficiency has been linked to spontaneous type I interferon (IFN) signaling. Few studies have examined the role of RNA editing in vascular remodeling-associated diseases, including pulmonary arterial hypertension (PAH), a devastating disease that can lead to right heart failure and premature death. Hypothesis: ADAR1 mediated RNA editing plays a vital role in vascular diseases, particularly the pathogenesis of PAH. Methods and Results: Deeply sequenced RNA-seq data analysis using the SOAP2 program showed that IPAH patient smooth muscle cells (SMCs, N=3) have shown significantly fewer editing sites in transcripts than healthy SMCs (N=3) & decreased levels of ADAR1 mRNA and protein. ADAR1 knockdown in healthy donor SMCs resulted in increased proliferation, migration and contractility, along with upregulated expression of IFN-b signaling-related molecules, such as MDA5 and ISG15. Furthermore, overexpression of MDA5, a dsRNA sensor of ADAR1-mediated immune response, in healthy SMCs induced activation of IFN-b signaling. A novel transgenic mouse model (ADAR1 SMC-KO ) was generated by knocking down ADAR1 (ADAR1 fl/fl ) selectively in smooth muscle actin-positive SMCs (SMA-CreER). Compared to controls, ADAR1 SMC-KO mice that underwent 3wk hypoxia developed severe pulmonary hypertension as evidenced by high RVSP (37mmHg, Fig1A) & RVH(FI: 42%, Fig1B) with the excessive vascular remodeling in distal vessels. They also expressed higher expression of IFN-b in serum and increased recruitment of inflammatory cells, including macrophages and monocytes(Fig1C). Conclusions: This study reveals a novel molecular mechanism of ADAR1 contributing to abnormal vascular remodeling mediated by upregulation of Type 1 IFN-b, which could be central to the pathobiology of PAH.