Role for RUNX2/HDAC6 Axis in Pulmonary Arterial Hypertension

Abstract

IntroductionPulmonary arterial hypertension (PAH) is a vascular remodeling disease characterized by enhanced pulmonary artery smooth muscle cells (PASMC) proliferation, migration, calcification and suppressed apoptosis. Numerous biological pathways have been implicated in this phenotype, including HIF‐1α. Recent studies have shown that miR‐204 downregulation upregulates the expression of RUNX2. RUNX2 is implicated in many features seen in PAH‐PASMC in part through the activation of HIF‐1α by a HDAC6‐depepdent mechanism. Thus we hypothesis that miR‐204‐dependent upregulation of RUNX2/HDAC6 axis promotes HIF‐1α and development of PAH.ResultsUsing human lungs, distal PAs and isolated PASMC from both control and PAH patients, we demonstrated a significant upregulation of RUNX2 and HDAC6 in PAH. Gain and loss of functions experiments in PASMC showed that downregulation of miR‐204 in controls PASMC increase RUNX2 expression, while increases miR‐204 in PAH‐PASMC decrease it. In controls PASMC, RUNX2 upregulation increases calcification,migration, proliferation, resistance to apoptosis through an HDAC6 and HIF‐1α dependent mechanism, as both tubastatin A (HDAC6 inhibitor) and siHIF‐1α blocks RUNX2 effects. Similarly in PAH‐PASMC siRUNX2 has the opposite effects. Finally, in sugen/hypoxia rat model of PAH, nebulization of siRUNX2 decreased mean PA pressure, pulmonary vascular resistance and increased compliance and cardiac output.ConclusionTaken together, our study uncovers a new miR‐204 dependent up regulation of RUNX2/HDAC6 axis contributing to calcification and to normoxic activation of HIF‐1α leading to proliferation, migration and resistance to apoptosis in PAH‐PASMC.