Long Noncoding RNA Rps4l Mediates the Proliferation of Hypoxic Pulmonary Artery Smooth Muscle Cells

Pulmonary hypertension (PH) is a rare and fatal disorder involving the vascular remodeling of pulmonary arteries mediated by the enhanced proliferation of pulmonary artery smooth muscle cells (PASMCs). Long noncoding RNAs are a subclass of regulatory molecules with diverse cellular functions, but their role in PH remains largely unexplored. We aimed to identify and determine the functions of long noncoding RNAs involved in hypoxia-induced PH and PASMC proliferation. RNA sequencing in a hypoxic mouse model identified hypoxia-regulated long noncoding RNAs, including Rps4l. Rps4l expression was significantly reduced in PH-model mice and hypoxic PASMCs. The subcellular localization of Rps4l was detected by RNA fluorescence in situ hybridization and quantification of nuclear/cytoplasmic RNA. Rps4l overexpression rescued pulmonary arterial hypertension features, as demonstrated by right ventricle hypertrophy, right ventricular systolic pressure, hemodynamics, cardiac function, and vascular remodeling. At the cellular level, Rps4l overexpression weakened cell viability and proliferation and suppressed cell cycle progression. Potential Rps4l-binding proteins were identified via RNA pull-down followed by mass spectrometry, RNA immunoprecipitation, and microscale thermophoresis. These results indicated that Rps4l is associated with and affects the stabilization of ILF3 (interleukin enhancer-binding factor 3). Rps41 further regulates the levels of HIF-1α and consequently leads to hypoxia-induced PASMC proliferation and migration. Our results showed that in hypoxic PASMCs, Rps4l expression decreases due to regulation by hypoxia. This decrease affects the proliferation, migration, and cell cycle progression of PASMCs through ILF3/HIF-1α. These results provide a theoretical basis for further investigations into the pathological mechanism of hypoxic PH and may provide insight for the development of novel treatments.