Neonatal hypoxia promotes pulmonary hypertension by upregulating ALKBH5 expression

Abstract

Postnatal hypoxia in high-altitude regions drives pulmonary developmental impairment in neonates, which may subsequently progress to pulmonary hypertension and right ventricular failure. N6-methyladenosine (m6A) RNA modification regulates mRNA fate and cellular responses to stress; however, its role in neonatal PH remains unknown. In this study, we established a neonatal rat model of PH by chronic hypoxia exposure and investigated the role of the m6A demethylase AlkB homolog 5 (ALKBH5) using pharmacological inhibition, siRNA knockdown, and integrated m6A‑seq/RNA‑seq. Hypoxia reproduced the key features of pulmonary developmental impairment and pulmonary hypertension, including alveolar simplification, reduced vascular density, increased medial wall thickness, elevated right ventricular systolic pressure, and right ventricular hypertrophy. Hypoxia increased ALKBH5 protein in pulmonary vascular smooth muscle, which was inhibited by an ALKBH5 inhibitor 5-Carboxy-8-hydroxyquinoline. In pulmonary artery smooth muscle cells (PASMCs), hypoxia increased ALKBH5 protein levels. ALKBH5 knockdown increased total m6A levels and suppressed proliferation and migration of PASMCs. Integrated MeRIP-seq/RNA-seq identified enolase 2 (ENO2) as a downstream target of ALKBH5 in PASMCs. ALKBH5 knockdown decreased ENO2 mRNA stability; ENO2 overexpression rescued proliferation and migration suppressed by ALKBH5 knockdown in PASMCs. Furthermore, hypoxia increased ALKBH5 promoter activity and expression via hypoxia-inducible factor-1 alpha (HIF-1α), thereby promoting proliferation of PASMCs and pulmonary vascular remodeling. Targeting the HIF-1α/ALKBH5/ENO2 axis may represent a therapeutic strategy for neonatal PH.