The role of RNA m(6)A methylation in the regulation of postnatal hypoxia-induced pulmonary hypertension

BACKGROUND: Pulmonary hypertension (PH) is a complex pulmonary vascular disease characterized by an imbalance in vasoconstrictor/vasodilator signaling within the pulmonary vasculature. Recent evidence suggests that exposure to hypoxia early in life can cause alterations in the pulmonary vasculature and lead to the development of PH. However, the long-term impact of postnatal hypoxia on lung development and pulmonary function remains unknown. N(6)-methyladenosine (m(6)A) regulates gene expression and governs many important biological processes. However, the function of m(6)A in the development of PH remains poorly characterized. Thus, the purpose of this investigation was to test the two-fold hypothesis that (1) postnatal exposure to hypoxia would alter lung development leading to PH in adult rats, and (2) m(6)A modification would change in rats exposed to hypoxia, suggesting it plays a role in the development of PH. METHODS: Twenty-four male Sprague–Dawley rats were exposed to a hypoxic environment (F(i)O(2): 12%) within 24 h after birth for 2 weeks. PH was defined as an increased right ventricular pressure (RVP) and pathologic changes of pulmonary vasculature measured by α-SMA immunohistochemical staining. Methylated RNA immunoprecipitation sequencing (MeRIP-seq) was performed to analyze m(6)A modification changes in lung tissue in 2- and 9-week-old rats that were exposed to postnatal hypoxia. RESULTS: Mean pulmonary arterial pressure, lung/body weight ratio, and the Fulton index was significantly greater in rats exposed to hypoxia when compared to control and the difference persisted into adulthood. m(6)A methyltransferase and demethylase proteins were significantly downregulated in postnatal hypoxia-induced PH. Distinct m(6)A modification peak-related genes differed between the two groups, and these genes were associated with lung development. CONCLUSIONS: Our results indicate postnatal hypoxia can cause PH, which can persist into adulthood. The development and persistence of PH may be because of the continuous low expression of methyltransferase like 3 affecting the m(6)A level of PH-related genes. Our findings provide new insights into the impact of postnatal hypoxia and the role of m(6)A in the development of pulmonary vascular pathophysiology.