The HIF‐1α/miR‐26a‐5p/PFKFB3/ULK1/2 axis regulates vascular remodeling in hypoxia‐induced pulmonary hypertension by modulation of autophagy

Abstract Pulmonary arterial hypertension (PAH) is a progressive and life‐threatening disease characterized by pulmonary vascular remodeling, which may cause right heart failure and even death. Accumulated evidence confirmed that microRNA‐26 family play critical roles in cardiovascular disease; however, their function in PAH remains largely unknown. Here, we investigated the expression of miR‐26 family in plasma from PAH patients using quantitative RT‐PCR, and identified miR‐26a‐5p as the most downregulated member, which was also decreased in hypoxia‐induced pulmonary arterial smooth muscle cell (PASMC) autophagy models and lung tissues of PAH patients. Furthermore, chromatin immunoprecipitation (ChIP) analysis and luciferase reporter assays revealed that hypoxia‐inducible factor 1α (HIF‐1α) specifically interacted with the promoter of miR‐26a‐5p and inhibited its expression in PASMCs. Tandem mRFP‐GFP‐LC3B fluorescence microscopy demonstrated that miR‐26a‐5p inhibited hypoxia‐induced PAMSC autophagy, characterized by reduced formation of autophagosomes and autolysosomes. In addition, results showed that miR‐26a‐5p overexpression potently inhibited PASMC proliferation and migration, as determined by cell counting kit‐8, EdU staining, wound‐healing, and transwell assays. Mechanistically, PFKFB3, ULK1, and ULK2 were direct targets of miR‐26a‐5p, as determined by dual‐luciferase reporter gene assays and western blots. Meanwhile, PFKFB3 could further enhance the phosphorylation level of ULK1 and promote autophagy in PASMCs. Moreover, intratracheal administration of adeno‐miR‐26a‐5p markedly alleviated right ventricular hypertrophy and pulmonary vascular remodeling in hypoxia‐induced PAH rat models in vivo. Taken together, the HIF‐1α/miR‐26a‐5p/PFKFB3/ULK1/2 axis plays critical roles in the regulation of hypoxia‐induced PASMC autophagy and proliferation. MiR‐26a‐5p may represent as an attractive biomarker for the diagnosis and treatment of PAH.