Xu et al. observed that hypoxia was strongly correlated with increased histone acetylation and hypoxia inducible factor-1α (HIF-1α) binding levels in the endothelin-1 (ET-1) gene core promoter region in a hypoxic pulmonary hypertension rat model, further indicating the significance of epigenetic modifications in PAH and pulmonary vascular remodeling [49]. This evidence concerns the gene EDN1 and pulmonary arterial hypertension.