EPAS1 (Endothelial PAS Domain Protein 1) Orchestrates Transactivation of Endothelial ICAM1 (Intercellular Adhesion Molecule 1) by Small Nucleolar RNA Host Gene 5 (SNHG5) to Promote Hypoxic Pulmonary Hypertension

EPAS1 (endothelial PAS domain protein 1), as the major effect gene for the adaptation to chronic hypoxia, is required for hypoxic pulmonary hypertension (HPH). Downregulated EPAS1 ameliorates the development of HPH. We confirmed that EPAS1-specific inhibitor PT2385 ameliorated HPH features, as demonstrated by right ventricle hypertrophy, right ventricular systolic pressure, and pulmonary vascular remodeling. However, the mechanism of EPAS1 in HPH pathogenesis remains unclear. RNA sequencing in human pulmonary artery endothelial cells with EPAS1 knockdown identified EPAS1-regulated genes, including ICAM1 (intercellular adhesion molecule 1), which created a proinflammatory perivascular microenvironment associated with HPH by elevating leukocyte adhesion to the vascular endothelium. Chromatin immunoprecipitation assays revealed that EPAS1 directly bound to ICAM1 promoter. The long noncoding RNA small nucleolar RNA host gene 5 (SNHG5), significantly increased in acute exacerbation period of chronic obstructive pulmonary disease and hypoxic human pulmonary artery endothelial cells, also contributed to the regulation of ICAM1 expression. Endothelial-specific deletion of Snhg5 also rescued HPH in mice. Overexpression of EPAS1 or SNHG5 enhanced, while the depletion of EPAS1 or SNHG5 attenuated, ICAM1 transactivation. SNHG5 was directly regulated by EPAS1, and interestingly, the upregulated SNHG5 could further enhance the levels of EPAS1, which consequently led to hypoxia-induced ICAM1 transactivation. RNA pull-down assay followed by high-throughput sequencing demonstrated that miR-625-5p could bind to SNHG5. Manipulating miR-625-5p altered the levels of EPAS1 during hypoxia. Our data showed a positive feed-forward exists between EPAS1 and SNHG5 signaling during hypoxia-induced ICAM1 transactivation in endothelial cells. Targeting EPAS1 and SNHG5 may provide promising strategies for the prevention of HPH.