Objective: Persistent pulmonary hypertension of the newborn (PPHN) is a major clinical problem. Nitric oxide produced by endothelial nitric oxide synthase (eNOS) in endothelial cells plays an important role in the pathogenesis of PPHN. The eNOS expression in endothelial cells is controlled by epigenetic regulation. The aim of this study was to investigate the epigenetic regulatory mechanisms of the eNOS gene in PPHN.
Methods: The rat model of PPHN was induced by hypoxia and indomethacin. Pulmonary vascular endothelial cells were isolated from the fetal rat lungs by magnetic-activated cell sorting. Chromatin immunoprecipitation and bisulfite sequencing methods were used to analyze epigenetic regulation.
Results: The levels of acetylated histone H3 and acetylated histone H4 at the proximal promoter of the eNOS gene in pulmonary vascular endothelial cells from PPHN were significantly higher than those from the control group (P < 0.01, respectively). Total methylation percentage of the eNOS gene promoter in PPHN rat was slightly lower than that of control, but there was no statistically significant difference between the two groups (24.7 ± 2.0 vs. 27.3 ± 2.3%, P = 0.408). These changes of epigenetic modifications at the eNOS gene promoter were consistent with increased levels of eNOS mRNA and protein in PPHN.
Conclusion: The increased expression of eNOS in PPHN was associated with epigenetic regulation.